WO1997024265A1

WO1997024265A1 - Hot-fill deformation-resistant polyester container

Info

Publication number: WO1997024265A1
Application number: PCT/CH1996/000452
Authority: WO
Inventors: Didier Apcher
Original assignee: Jean Gallay S.A.
Priority date: 1995-12-29
Filing date: 1996-12-20
Publication date: 1997-07-10
Also published as: FR2743050A1; FR2743050B1

Abstract

The container (20) has at least one shrinkage window (21) comprising a central panel (22) and a deformable frame (23) completely enclosing the central panel. Said frame consists of a protective surround that forms a junction wall between the central panel (22) and the adjacent wall (24) of the container (20). The protective surround comprises two folds (25, 26) constituting a material reserve to be deployed when the central panel (22) moves to adopt a new parallel position after the liquid within the container has cooled. The central panel (22) is of sufficient rigidity to move as an entity. Such rigidity is obtained, for example, by having a material thickness greater than that of the frame.

Description

POLYESTER CONTAINER, HOT-FILLABLE AND RESISTANT TO DEFORMATION

The present invention relates to a plastic container produced by a blowing process intended to contain a substance, in particular a liquid and in particular a drink, comprising on at least one of its walls, at least one withdrawal window arranged to compensate for the loss in volume of said substance after it has cooled, said withdrawal window comprising a central panel

This type of container is generally made of a thermoplastic synthetic material and more particularly of PET (polyethylene terephthalate) according to a blowing process from a molded preform

Certain receptacles of this type, and in particular bottles, are intended to be filled hot with a liquid reaching temperatures of the order of 85 to 95 ° C. They must therefore withstand the filling temperature and have resistance to cold enough to prevent collapse

The temperature resistance of the bottle is obtained by a modification of the physical structure of the material, this modification being effected during blowing. The blowing takes place in a hot mold, the contact, maintained by means of the blowing pressure, between the blown plastic and the hot mold causing the desired structural modification. The combined management of the mold temperature and of the time the material remains in pressure against the walls of the mold, makes it possible to obtain more or less significant heat resistance properties as required. The cooling of the bottle is done by injection of gaseous fluid at low temperature inside the bottle, this gaseous fluid can be cold air, carbon dioxide or nitrogen or by transfer of the bottle into a mold cooler than the first. Various techniques are known and allow the desired results to be obtained.

The hot filling of the bottle is carried out as follows: - in a first step, the bottle is filled with the hot liquid, the temperature of which is around 85 to 95 ° C.

- in a second stage, which immediately follows the first, the bottle is capped

- In a third step, the bottles are passed through a cooling tunnel to bring them to room temperature.

During this third step, the liquid contained in the bottle decreases in volume. However, the bottle being closed, the loss of volume of the contents generates a vacuum or aspiration which results in a tendency for the bottle to contract, a phenomenon which is called collapse. This phenomenon deforms the bottle which tends to collapse on itself if precautions are not taken at the time of its construction. To avoid this crushing, the bottles are provided with contraction zones which are called withdrawal windows. These areas have in principle the ability to retract, compensating for the loss of volume of the liquid and making it possible to avoid collapse, so that the rest of the bottle does not deform.

The efficiency of these windows is not optimal, because they are linked to the rest of the bottle which, in turn, must absolutely not deform. Because of this connection, the mobility of the windows is very limited, the deformation being located mainly in the central part of these windows, and remaining very slight in the vicinity of their periphery. Therefore, the active surface of the windows represents only a reduced proportion of their total surface.

For example, for a 500 cm ³ bottle, the change in volume of the liquid content going from 85 ° C to 20 ° C is of the order of 15 cm ³ . Doing abstracting from the withdrawal of the bottle itself after filling, it is essential that the bottle can, through its withdrawal windows, absorb a reduction in volume of 15 cm ³ The bottles of approximately circular shape can have six windows evenly distributed around their periphery, if it is assumed that these windows have a width of 0.0024 m and a height of 0.0055 m, that is to say an area of 13.2 × 10 ⁻⁶ m ^2. As long as all the windows act in the same way, each of them must be able to compensate for 2.5 cm ^3. If we consider that approximately 50 to 60% of each window is really active, the active surface per window will be between 6.6 and 7.92 x 10 ^"6 m ² . Assuming that the withdrawal windows move parallel to themselves, which is not usually the case, they should move inwards from 3.78 to 3.15 x 10 ^"3 m .

Since the withdrawal windows have only a small active surface in relation to their total surface, the deformation of this active part must be greater than that which would occur if the entire surface of the window contributed to compensating for the reduction in volume, and the risk of deformation of the parts of the bottle other than the active parts of the windows and in particular of the parts arranged between the windows is far from negligible. To avoid this risk, blowing methods have been developed which allow the thickness distribution to be controlled very precisely and special bottles for hot filling are produced, the walls of which are considerably thicker than those of bottles filled with cold. For example, a 0.5 liter bottle, intended to contain a cold filled liquid, weighs on average 25 x 10 ^'3 kg and a similar bottle for a hot filled bottle weighs on average 35 x 10 ^"3 kg.

The surplus material consumption is relatively large so that the cost of these special bottles is high compared to the average cost of standard bottles for cold filling. Certain containers have been studied to allow deformation of the withdrawal windows while avoiding deformation of the areas arranged between these windows, without increasing the amount of material used. Such a container is notably described in the American patent published under the number US-A -4 805 788 This container has longitudinal grooves along the two vertical edges of the windows, these edges being intended to increase the rigidity of the areas of the container disposed between the windows

This embodiment implies that the edge of the windows remains practically immobile during the cooling of the liquid. Only a small amount of the window surface deforms and adapts to the decrease in volume. It is therefore essential that the windows occupy a large surface of the body of the container, which decreases the width that the areas between the windows could have and consequently reduces the rigidity of the container. It is therefore not possible to guarantee good stability of the general shape of the container when the variation in volume is significant during cooling of the liquid.

The present invention proposes to overcome these drawbacks by producing a container specially designed to allow you to fill hot liquids without the need to increase the thickness of its walls, while allowing a significant variation in the volume of the liquid and ensuring good stability of the container shape.

To this end, the container according to the invention is characterized in that the central panel is entirely surrounded by a deformable frame, the deformation of the frame being such that it generates an overall radial displacement of the central panel towards the interior of the container. , so that this central panel moves substantially parallel to itself According to an advantageous embodiment, said deformable frame is constituted by an entourage of the central panel forming a junction wall between said central panel and the adjacent wall of the container, this junction wall being arranged in planes forming an angle substantially between 45 and 90 ° relative to the plane tangent to said central panel.

Preferably, said deformable frame is constituted by an entourage of the central panel forming a junction wall between said central panel and the adjacent wall of the container, this junction wall comprising at least one fold arranged to stretch laterally relative to to the overall radial displacement of the central panel.

Advantageously, said deformable frame is thinner than the other parts of the walls of the container and said central panel is rigid and has a thickness greater than that of the deformable frame.

According to an advantageous variant, said central panel of the withdrawal window comprises at least two layers distant from each other.

In this variant, said layers have decreasing thicknesses from the outside to the inside.

The present invention will be better understood with reference to the description of an embodiment and its variants and the appended drawing in which:

FIG. 1 represents an elevation view of a known bottle provided with withdrawal windows,

FIG. 2 represents the bottle of FIG. 1, seen in cross section, FIG. 3A represents a cross-sectional view of a window for withdrawing a container according to the invention, when a hot substance is introduced into it,

FIG. 3B represents a view similar to that of FIG. 3A, when the substance has cooled and when the withdrawal window has retracted,

FIGS. 4A and 4B represent views similar to those of FIGS. 3A and 3B, but corresponding to another embodiment of a withdrawal window,

FIGS. 5A and 5B are also views similar to those of FIGS. 3A and 3B, but corresponding to an alternative embodiment of a withdrawal window, and

- Figures 6A and 6B show a variant in which the withdrawal window comprises at least two layers.

Referring to Figures 1 and 2, the container 10 shown is a bottle made from a preform according to a blowing process. It has on its side walls a series of withdrawal windows 11 which appear as substantially rectangular areas slightly concave towards the inside of the bottle. These windows preferably have a thickness less than that of the adjacent walls 12 of the bottle. Each of these windows has an active surface 13 which represents only part of their total surface. The active surface is in fact the part of the surface of the withdrawal window which deforms under the effect of the reduction in volume of the substance contained in the bottle after cooling.

It can be seen in FIG. 2 that the shrinkage is particularly marked in the central zone 14 and that it gradually decreases to become zero at the edges 15 of the window The interior of the window is attached to the adjacent walls by relatively rigid inclined edges 16, which prevents the overall removal of the window in favor of a partial removal of a central part called the active surface

Figures 3A and 3B show a preferred embodiment of a container withdrawal window according to the invention. The container 20 has at least one withdrawal window 21 which consists of a central panel 22 and a deformable frame 23 which completely surrounds this central panel. The deformable frame is an entourage forming a junction wall between the central panel 22 and the adjacent wall 24 of the container 20. It will be noted that this central panel moves parallel to itself as precisely shown in FIG. 3B, to occupy a position 22a after the substance contained in the container has cooled. We see in your practice that it is essentially the second fold 26 which works and allows the withdrawal of the window parallel to itself. This fold has the necessary flexibility, for example thanks to a reduced thickness of material, to be able to deploy and open and allow the radial movement of the central panel. This central panel has adequate rigidity to move globally. This rigidity can, for example, be obtained by a thickness of material greater than that of the frame.

FIGS. 4A and 4B illustrate an embodiment of a container 30 having at least one withdrawal window 31 provided with a central panel 32 and a deformable frame 33. The deformable frame in this case constitutes a junction wall between the central panel and the adjacent wall of the container, this junction wall being disposed in planes forming an angle a between 45 and 90 ° and preferably close to 45 to 60 ° relative to a plane tangent to said central panel. It can be seen that the displacement of the withdrawal window 32 in a position 32a results in an opening of the angle a. FIGS. 5A and 5B show an alternative embodiment deriving from the construction represented by FIGS. 3A and 3B. A container 40 has at least one withdrawal window 41 with a central panel 42 and a deformable frame 43 In this case, the deformable frame which defines a junction wall between the central panel and the adjacent wall of the container consists of a pleating or of a succession of folds 44, 45, 46, 47 which can stretch laterally or open to allow the central panel to move radially towards the interior of the container to occupy a withdrawal position 42a.

FIGS. 6A and 6B illustrate a variant of a container 50 according to which the withdrawal window 51 comprises two or more layers 52, 53 superposed. These superimposed layers have decreasing thicknesses from the outside to the inside, so that their sensitivity is increasing. In this way, it is possible to control the vacuum inside the bottles almost completely and we can achieve zero vacuum at the end of the content cooling.

As before, the layers 52 and 53 move parallel to themselves and take positions of withdrawal 52a and 53a visible in FIG. 6B.

Other embodiments are possible. The window or more generally the withdrawal windows can be formed in the side walls of the container, but it is also possible to arrange them in the bottom of this container. Their number and size may vary depending on the size of the container and its shape. For a bottle of circular section, it is advantageous to arrange the windows evenly around the periphery of its side wall.

Claims

1 container made of synthetic material produced by a blowing process, designed to contain a substance, in particular a liquid and in particular a drink, comprising on at least one of its walls, at least one withdrawal window (21, 31, 41, 51) arranged to compensate for the loss of volume of said substance following its cooling, said withdrawal window comprising a central panel, characterized in that this central panel is entirely surrounded by a deformable frame (23, 33, 43), the deformation of the frame being such that it generates an overall radial displacement of the central panel (22, 32, 42) towards the interior of the container, so that this central panel moves substantially parallel to itself

2 container according to claim 1, characterized in that said deformable frame (23, 33, 43) is constituted by an entourage of the central panel forming a junction wall between said central panel (22, 32, 42) and the adjacent wall of the container, this junction wall being arranged in planes forming an angle substantially between 45 and 90 ° relative to the plane tangent to said central panel

3 container according to claim 1, characterized in that said deformable frame (23, 33, 43) is constituted by an entourage of the central panel (22, 32, 42) forming a junction wall between said central panel and the adjacent wall of the container, this junction wall comprising at least one fold arranged to stretch laterally with respect to the overall radial displacement of the central panel

4 container according to claim 1, characterized in that said deformable frame is thinner than the other parts of the walls of the container

5. Container according to claim 1, characterized in that said central panel (22, 32, 42) is rigid and has a thickness greater than that of the deformable frame (23, 33, 43).

6. Container according to claim 1, characterized in that said central panel of the withdrawal window (51) comprises at least two layers (52, 53) spaced from one another.

7. Container according to claim 6, characterized in that said layers (52, 53) have decreasing thicknesses from the outside to the inside.