EP0998424A1

EP0998424A1 - Method for filling containers and installation therefor

Info

Publication number: EP0998424A1
Application number: EP98939709A
Authority: EP
Inventors: Gérard Emmer
Original assignee: Sidel SA
Current assignee: Sidel SA
Priority date: 1997-07-22
Filing date: 1998-07-20
Publication date: 2000-05-10
Anticipated expiration: 2018-07-20
Also published as: AU747687B2; JP2001510768A; KR20010022035A; ES2189221T3; CA2297267C; BR9811520A; DE69810116D1; WO1999005061A1; FR2766473A1; AU8812898A; FR2766473B1; DE69810116T2; US6220310B1; EP0998424B1; ATE229473T1; CA2297267A1; CN1265079A; JP3361797B2

Abstract

A method for filling a plastic container (8) while it is still hot and deformable without damaging it, when the filling comprises a phase (17; 13) during which a noticeable difference in pressure between the container inside and the environment external to the filling installation occurs, at least during part of said phase, consisting in placing the container in a sealed chamber (9) isolating it from the external environment and modifying (18; 12) the pressure inside the chamber to reduce, even cancel, the difference in pressure between the container inside and outside. The invention is applicable to the filling of plastic containers, with aerated beverages and/or their filling after a vacuumizing phase of their internal volume, immediately after they have been made by blowing.

Description

PROCESS FOR FILLING CONTAINERS. AND INSTALLATION FOR IMPLEMENTATION.

The invention relates to improvements made to the filling of plastic containers when this operation comprises at least one step during which a significant pressure difference occurs between the interior of the container and the environment outside the filling installation, and when this operation is carried out while the containers are hot and have more or less malleable zones. This is the case when the filling phase of the container with any product is preceded by a vacuum

(more or less pronounced vacuum) of the interior of the container when filling with beer in particular, or of an overpressure when filling with a carbonated liquid, and when the containers are filled immediately after their manufacture by blowing or drawing and then blowing a blank. It relates to a method and an installation for its implementation.

The filling of a container with any product can sometimes be preceded by a vacuum or pronounced depression of the interior of the container, for example to replace the air therein by another medium so as not to do not denature the product which will finally be packaged in the container. This is, for example, the case when filling oxy-sensitive products such as beer, certain fruit juices or others: all traces of oxidizing product must be removed, and inerting is then carried out with nitrogen, for example .

The filling of a container, such as a bottle, with a carbonated liquid conventionally consists of a phase of pressurizing the interior of the bottle with a gas, typically carbon dioxide, followed by a filling phase with the liquid, and a phase of depressurization to remove excess gas, while still maintaining a certain gas pressure therein.

The difference in pressure causes problems on plastic containers, when the filling operation is attempted a few seconds after the containers have been taken out of the blow mold and are still hot, as is the case in so-called online filling installations.

With these containers, it is not possible to achieve a vacuum prior to filling, without causing deformation by collapsing or collapsing of the containers.

With this same type of container, filling with carbonated liquids poses the following problem: the phase of pressurization of the containers before filling causes them to burst or an irreversible deformation.

The deformations or bursts affect the body of the containers, but there are deformations affecting more particularly the bottoms of the containers

(cracking phenomena called "stress crac ing" in the language of the trade).

These phenomena are due to the fact that a plastic container is obtained by blowing a blank (preform, parison, intermediate container) previously brought to its blowing temperature, therefore softened, by heating. When the container leaves the blow mold, there remain more or less hot zones, therefore more or less malleable zones. Generally, it is the areas that have been least stretched during blowing that cool the slowest for various reasons. And the bottom is one of the least stretched areas. However, if while the pressure difference is present, the temperature still exceeds the softening temperature, deformation can occur due to the mechanical stress exerted on these areas, by internal pressure (overpressure or depression).

It still happens, but however less often, that bursts or deformations occur when the filling takes place without depression or prior overpressure with a gas, but when the pressure of introduction of the liquid or, more generally, of the product of filling is quite high.

In fact, the plastic containers, and therefore their blanks, are sized to withstand the internal pressure values (overpressure or depression) necessary for their filling or for the conservation of the products after capping when the material is stabilized, therefore cooled.

This is why, until now, all the tests of filling, under the aforementioned conditions, of plastic containers still having zones at a temperature higher than the softening temperature and dimensioned to resist the same conditions when the material is stabilized, ended in failure, and line filling was not applied to them industrially.

One possible solution consisted in oversizing the containers to compensate for the deformability by an excess of material. This solution is however not realistic for various reasons, among which: on the one hand, it goes against the current trend which is the reduction in the weight of containers, for reasons of material cost; on the other hand, the containers obtained are quite unsightly; moreover, paradoxically, the excess of material makes the containers fragile when they are stabilized; finally, the excess material, necessary for filling, becomes unnecessary when the containers are cooled.

The invention aims to remedy these drawbacks, and to allow the filling of containers sized to hold the filling pressures when they are cold, but deformable at least during part of the filling.

According to the invention, a method for avoiding the irreversible deformation or deterioration of a plastic container comprising at least one zone whose temperature exceeds the softening temperature of the material, during a filling operation comprising a phase during from which a significant pressure difference exists between the interior of the container and the environment outside the filling installation, is characterized in that, at least during part of said phase, as long as it is not stabilized thermally and is still deformable, the container is placed in a sealed enclosure isolating it from the outside environment, the pressure inside the enclosure is modified with respect to the outside atmosphere so as to reduce or even cancel the difference pressure between the inside and the outside of the container.

Thus, by reducing or even canceling the pressure difference which exists between the interior and the exterior of the container, as long as the material is not thermally stabilized, the risks of bursting or deformation are eliminated, and it is possible to filling while the container still has malleable areas.

According to another characteristic, when the pressure difference between the interior of the container and the external environment is obtained by creating a vacuum in the container, the pressure inside the enclosure is modified by reducing it to bring it closer to, or even reach that of the interior of the container.

Preferably, the pressure reduction inside the enclosure and that inside the container are carried out simultaneously.

According to another characteristic, the filling product is a carbonated liquid and the modification of the pressure is carried out by injecting a pressurized fluid into the enclosure isolating the container from the external environment. In this case, the arrival of the filling liquid promotes cooling of the container which then stabilizes quickly.

According to another characteristic, the fluid is a gas. In one implementation, when the liquid is gasified, the pressure is changed using the gas used for gasification (carbon dioxide in particular).

In this case, it is easy to achieve a pressure balance between the inside and the outside of the container by simultaneously modifying the pressures in the container and in the enclosure and the problems of bursting or deformation.

Other characteristics and advantages of the invention will appear on reading the description which follows, given with reference to the appended figures, in which:

Figure 1 schematically illustrates the different phases of filling with gasification with resistant containers;

- Figure 2 schematically illustrates the principle of the invention applied to filling with a carbonated liquid; - Figure 3 schematically illustrates the principle of the invention applied to the prior depression of the interior of a container;

- Figure 4 schematically illustrates the principle of the invention applied to a prior depression of a container followed by filling with a carbonated liquid;

Figures 5 and 6 illustrate two possible embodiments of an installation for implementing the invention, for filling with a carbonated liquid;

- Figure 7 is a schematic view, from above, of an installation for implementation;

- Figures 8 and 9 are schematic views of variants of a part of the installation for the implementation of the invention;

FIG. 10 illustrates an advantageous embodiment of part of FIGS. 8 and 9.

Referring to FIG. 1, a known cycle for filling a container with a carbonated liquid, such as a carbonated liquid, typically comprises the following phases.

1) A "phase 1" during which the container, here a bottle 1, is introduced into the filler and is positioned so that its neck 2 is located opposite a filling head 3. When the bottle 1 is made of plastic, it is held, during the various phases, under its neck 2, using appropriate means, such as pliers 4, this to avoid that during the subsequent phases, the bottle 1 does not collapse under the effect of the pressing force exerted by the head 3. 2) A "phase 2" during which the bottle 1, and more precisely its neck 2 is centered with respect to the filling head 3 and the latter is pressed against the neck to ensure the seal;

3) a "phase 3" of placing the internal pressure in the bottle 1 using an appropriate gas, typically carbon dioxide or a gas occurring naturally in the liquid. This internal pressurization phase is carried out by injecting the gas through conduit (s) opening into the filling head 3. It is shown diagrammatically by arrow 5 in the figure;

4) a "phase 4" filling through the filling head 3 (arrow 6 in the figure);

5) a "phase 5" evacuation of excess gas in the container (arrow 7). During this phase, the excess gas can be returned to the tank from which it was injected during phase 3;

6) a "phase 6" of releasing the head 3 for filling and evacuating the full bottle 1 still maintained by the clamps 4 under its neck 2.

It is generally during phase 3 (pressurization) and / or phase 4 (filling) that the bursting or deformation problems mentioned in the preamble arise.

Of course, during filling without prior gas injection, phases 3 and 5 do not exist. It is during the filling phase (phase 4) that problems can arise, especially if the filling pressure and / or flow rate is (is) too high.

FIG. 2 illustrates the principle of the process of the invention applied to the filling of containers in plastic, such as bottles, with carbonated liquids, such as carbonated drinks.

The process can be summarized in three phases illustrated by diagrams 2-1, 2-2 and 2-3.

In Figure 2-1:

After the container 8, here a bottle, has been placed in a sealed enclosure 9, and its neck 10 has been placed in sealed communication with a filling head 11, gas is injected (arrow 12) inside the container 8 by a conduit opening into the head 11, and a fluid is injected (arrow 13) into the sealed enclosure by a conduit to exert a back pressure outside the container.

Preferably, the fluid used to exert the back pressure is a gas. A liquid could also be used, but this would considerably complicate the implementation of the invention: it would indeed be necessary, unless using a non-wetting liquid, to dry the outside of the containers after filling.

The moment when the fluid is injected into the enclosure 9 relative to that when the gas is injected into the container 8, as well as the relative values of the pressures inside and outside of the container do not matter: what It is essential that the pressure difference, at all times, is such that the container does not undergo bursting or deformation.

However, preferably, in order to facilitate the implementation of the method, the injection of the backpressure fluid and that of the gas takes place simultaneously.

Alternatively, it is possible to slightly shift the time when the pressure increase is started in the container 8 from that when it is started in enclosure 9, first starting to increase the pressure in the container and then starting in enclosure 9, before the pressure in the container is too high.

Then occurs the filling phase, through a conduit 14, in Figure 2.2, during which, preferably, the back pressure is maintained. Indeed, it is likely that at this stage the container is not yet stabilized.

Then follows (Figure 2.3) a degassing phase inside the container 8 (arrow 15 in this figure) and a release phase of the back pressure (arrow 16 in the same figure), before the container is removed from the machine. to be capped, or alternatively capped before leaving in case the machine is a filler-capper.

In one implementation, the back pressure is released just after the internal pressure is established, that is to say before filling or during filling. The process is however more random, and more difficult to control because if the container is not sufficiently stabilized, one can still witness deformations and / or bursts.

In another implementation, the release of the back pressure begins after the start of degassing, that is to say when it is certain that the stresses due to the pressure inside the container have completely disappeared. This solution offers maximum security, but significantly slows down the cycle time.

In one implementation, it is the entire installation which is under overpressure, in order to exert the counterpressure outside the containers. This solution is however cumbersome to manage, because it is necessary to provide means, such as airlocks, to allow the entry and exit of the containers without the overpressure significantly decreasing inside the installation.

This is why, preferably, as illustrated by FIGS. 3 to 7, each container introduced into the filling machine is enclosed in an enclosure making it possible to isolate it from the rest of the ambient atmosphere of the machine. When this enclosure is closed, the phases of gasification, back pressure, filling, degassing and release of the back pressure then occur.

Thus, if the containers are introduced one by one, one after the other, so that the containers undergo the different phases with an offset, each container is enclosed in a different enclosure from that which precedes it and that which it follows in the installation. On the other hand, if the containers are introduced in successive groups, then all the containers of the same group can be introduced simultaneously into the same enclosure, different from that of the preceding group or that of the following group. However, it is still possible that all the containers of the same group are introduced simultaneously into separate enclosures.

In Figure 3 is illustrated how the invention is applicable to the prior vacuuming of a container 8, and thus allows to achieve, with plastic containers still malleable, what the methods of the prior art do not allow.

After the container 8 has been trapped in the sealed enclosure 9, and its neck 10 has been placed in communication with the filling head 11, a depression (arrow 17) is created inside the container and is accompanied ( arrow 18) by a depression inside the enclosure to avoid collapsing of the container 8. The depressions in the enclosure 9 and in the container 8 can be of the same value and be carried out simultaneously. We can then achieve a pressure balance inside and outside the container.

Alternatively, it is possible to slightly shift the moment when the vacuum started in the container from that when it started in the enclosure, preferably by first starting to create a vacuum in the enclosure 9. Similarly, the final values of the depressions in the enclosure and in the container may not be equal. They must be adapted so that ultimately there is no unwanted deformation of the container.

After the vacuum in the container has taken effect (for the record, for example, preparation of inerting with nitrogen), ambient pressure can be restored inside the container 8 and the enclosure 9. For this, as illustrated in Figure 3.2, both the interior of the container 8 and that of the enclosure 9 are returned to the open air (arrows 19 and 20 respectively).

Preferably, to avoid any deformation of the container 8 at this stage, it can be returned to ambient pressure before the enclosure 9.

Then (figure 3.3), the container is filled (arrow 21). It is not essential, at this stage, that it be maintained in enclosure 9 since the internal pressure of enclosure 9 is equivalent to that of the external environment since the previous phase (figure 3.2), unless that the filling is not intended to gasify the content, which will be explained with reference to FIG. 4.

The container can then be capped and then disposed of.

As illustrated in Figure 4, the invention has the particular advantage that a single installation can be used to combine the two methods mentioned with reference to Figures 2 and 3 respectively.

The same elements have the same references.

After a container 8, in this case a bottle, has been placed in the sealed enclosure 9 (FIG. 4.1), a vacuum is created both inside the bottle (arrow 17) and inside the enclosure (arrow 18). .

Then (figure 4.2), the interior of the bottle and that of the enclosure are put back to the pressure of the external environment (arrows 19 and 20), then (figure 4.3), the interior of the bottle and that of the enclosure can be pressurized (arrows 12 and 13) before the bottle is filled (arrow 14 in figure 4.4).

Then (figure 4.5), the pressures inside the enclosure and the bottle can be released (arrows 15 and 16), before the full bottle has come out of the enclosure (figure 4.6).

It is therefore understandable that an installation for implementing the method according to the invention can be very simple to carry out: it suffices to provide a sealed enclosure with the appropriate conduits to create a vacuum in the enclosure and the container and / or to overpress the interior of the enclosure and the interior of the container.

Figures 5 and 6 schematically illustrate two possible embodiments of installations for implementing the method of the invention. More specifically, these figures show the parts of the installations used for filling with the container being evacuated and / or internal overpressure.

In these figures, online filling installations have been shown, in which the containers are moved continuously. The invention is, of course, applicable to other types of installations.

The difference between Figures 5 and 6 is as follows:

- In the embodiment of FIG. 5, the fluid for overpressuring the enclosure associated with a container is different from that used for the overpressure of the interior of the container. The enclosure can be pressurized with compressed air while the container is pressurized with gas to gasify the filling product (for example carbon dioxide in the case of carbonated drinks);

- In the embodiment of Figure 6, it is the pressurization gas of the container which is also used to put the enclosure under pressure.

The latter solution has the advantage of allowing isopression between the enclosure and the container.

On the other hand, when the enclosure is opened, the quantity of gas remaining in the enclosure after degassing is lost.

It is therefore not economical with regard to gas consumption.

Due to the similarities between the two figures, similar or identical elements have the same references. Furthermore, in order to simplify the understanding of these figures, symbols have been associated with the various conduits, whenever necessary, showing the existence or not of a flow of liquid and / or gas (arrows indicating the existence and the direction of a flow, or line blocking a conduit, to indicate that said conduit is or must be closed, to prevent the passage of liquid or gas). The installations of FIGS. 5 and β are installations for filling in the procession of the containers, that is to say that each container, while being animated by a movement of continuous translation over a determined path, is put in contact with the means for evacuating and / or carrying out the pressurization on the one hand, and the filling means, on the other hand.

In Figures 5 and 6 are shown six containers (here bottles) 220; ...; 225, each associated with a separate enclosure and therefore with separate means for evacuating and / or pressurizing and filling.

Each enclosure is made up of two distinct parts, respectively a 230H upper part; ...; 235H forming a cover, and a lower part 230B; ...; 235B, forming a receptacle to receive the corresponding container. The dimensions of a receptacle 230B; ...; 235B, are such that when the cover 230H; ...; 235H is in place, the container is contained in the enclosure, as will be explained later.

The upper parts 230H; ...; 235H, as well as the lower parts 230B; ...; 235B, are fixed to the mobile structure 24 of the installation, so that all the upper parts 230H; ...; 235H follow the same route with a phase shift in time on the one hand, all the lower parts 230B; ...; 235B follow the same route with, again, a phase shift in time.

Furthermore, in the embodiments illustrated in Figures 5 and 6, each lower part 230B; ...; 235B can be moved away from the upper part (cover) 230H; ...; 235H corresponding, in particular during the phases of setting up or taking out of the containers. To this end, each lower part is associated with means such as a guide rod, respectively 250; ...; 255 sliding for example in a bearing 260; ...; 265 formed in the mobile structure 24.

Preferably, as illustrated by these FIGS. 5 and 6, the mobile structure 24 causes a displacement with a horizontal component of the upper and lower parts respectively, and the means 250; ...; 255; 260; ...; 265, cause a vertical translation of the lower parts 230B; ...; 235B with respect to the mobile structure during its movement in the direction of arrow 27, and therefore with respect to the upper parts 230H; ...; 235H.

For vertical translation, there is provided, for example, as illustrated by these Figures 5 and 6, a fixed cam 28 acting on a roller 290; ...; Respective 295, associated with each rod 250; ...; 255.

More specifically, the cam 28 is fixed to the chassis, not shown, of the installation, so that when the roller associated with a rod, and therefore at the bottom

(receptacle) corresponding, meets the fixed cam, it follows the profile imposed by the shape of the cam, causing a corresponding movement of the associated receptacle.

In the example illustrated by FIGS. 5 and 6, a first receptacle 230B is in the low position; the corresponding container 220 has just been loaded; the roller 290 is at the bottom of the cam.

The second receptacle 231B corresponding to the second container 221 is partially reassembled.

The next three 232B; ...; 234B are completely reassembled and in contact with their cover 232H; ...; 234H corresponding: the chambers are therefore closed, and the vacuum and / or pressurization, as well as the filling, can take place. The last receptacle 235B is finally being lowered, the corresponding bottle 225 being filled and being able to be released at the end of the lowering.

Alternatively, it could be envisaged that the lower parts are fixed relative to the movable structure 24, the upper parts being movable in vertical translation relative to this structure. This would considerably complicate the installation because, as illustrated in FIGS. 5 and 6, the upper parts are associated with filling heads 300; ...; 305 respective, with conduits not only for filling, but also for putting under vacuum and / or pressurizing the interior of the enclosure and / or the corresponding container, and with means for holding the containers.

Preferably, as illustrated in FIG. 7, the installation can be of the rotary type. The mobile structure 24 is then a carousel rotating around an axis of rotation 31, said carousel carrying the speakers more generally referenced at 23 with an upper part (cover) 23H and a lower part (receptacle) 23B, and the cam 28 of guiding the rollers 29 is then in an arc.

In a manner known per se, the containers are introduced one by one into the installation (entry materialized by arrow 320 in FIG. 7); they are gripped at their neck by pliers 330; ...; 335 respective, associated with each filling head 300; ...; 305 (the clamps are shown diagrammatically in FIGS. 5 and 6). The tongs are movable vertically, to press the rim of the containers against the filling head. The upward movement of each clamp takes place for example when the receptacle is being raised. This is symbolized by a rising arrow on the clamp 331 associated with the container 221. After filling and possible degassing of the container and of the associated enclosure, the corresponding clamp 335 descends, to release the neck of the container 225 from the filling head, before it leaves the installation (the exit zone is materialized by arrow 321 in Figure 7).

In order to avoid overloading FIGS. 5 and 6, only those have been illustrated there, among the conduits, which serve to ensure the internal overpressure of the enclosures and the containers and the filling of the latter. Similarly, the connection between these conduits and the sources of liquid and gas, or the sources themselves, has not been illustrated, since the person skilled in the art will be able to reconstruct these connections in the light of the description.

Each head 300; ...; 305 is crossed by a conduit 340; ...; 345 for the internal overpressure of the container (gasification) and through a conduit 350; ...; 355 for filling.

Furthermore, another conduit 360; ...; 365 is provided for the internal overpressure of the enclosure.

In Figure 5, the conduits 360; ...; 365 open into the lower part 230B; ...; 235B corresponding. Alternatively, as illustrated in Figure β, they open into the upper part 230H; ...; 235H.

In Figure 5, the conduits 340; ...; 345 for the gasification of the containers are independent of those 360; ...; 365 for the internal overpressure of the speakers. Thus, it is possible to put each enclosure under overpressure with a fluid distinct from the gas for the gasification of the filling product. For example, it is possible to use compressed air to put the interior of the enclosure under pressure. In Figure 6, each conduit 340; ...; 345 for the gasification of a container is associated (bypass) with the corresponding conduit 360; ...; 365 for the overpressure of the enclosure. Thus, the gas for the gasification of the container can also be used for the overpressure of the enclosure.

The overpressure and filling operations are carried out after closing the enclosure, in accordance with what has been described with reference to FIG. 3. In the example of FIGS. 5 and 6, the container 222 and the enclosure 232H, 232B corresponding are being pressurized; the container 223 is being filled, the pressure in this container and in the enclosure are maintained (which is shown by a line crossing the conduit 363 for pressurizing the enclosure), the container 224 is full, and the pressure is released both in the container and in the enclosure; finally, the lower part 235B of the enclosure associated with the container 225, full, is being lowered to allow the exit of this container.

In Figure 8, there is shown the block diagram of an improved upper part 23H adaptable to the embodiment of Figure 5, and further allowing vacuum in the container and in the enclosure.

In addition to the conduits, more generally designated by

34, for the gasification of the container 22, through the filling head 30, 36 for the overpressure of the enclosure, and 35 for filling through the head 30, two conduits are provided, respectively 37 for the evacuation of the enclosure and 38 for the evacuation of the container 22, through the head 30. These last two conduits are either connected together as illustrated in FIG. 8, which makes it possible to connect them to a common vacuum pump (not shown), either not interconnected and connected to separate pumps. Furthermore, the conduits 34 for the gasification of the contents and 36 for the pressurization of the enclosure are separated, allowing for example to put the enclosure under pressure using compressed air.

In FIG. 9, which is a block diagram of an improved upper part 23H adaptable to the embodiment of FIG. 6, while also making it possible to produce a vacuum in the enclosure and in the container 22, the same are found conduits as in FIG. 8, but the conduits respectively 34 for the gasification of the contents and 36 for the overpressure of the enclosure are connected together, allowing the enclosure to overpressure with the gasification gas.

A problem presented by the embodiments of FIGS. 5, 6, 8, 9 is that two 34, 35 or three 34, 35, 38 conduits pass through the filling head 30, which somewhat complicates its constitution.

This is why, in an embodiment illustrated in FIG. 10, provision is made for the conduits to be connected to a valve 39 with mechanical, electrical or other control 40.

An intermediate conduit 41 is connected to the head 30 and places this valve in communication with the interior of the container 22. By acting on the control 40, the interior of the container 22 is placed in communication with either the evacuation conduit 38 (when present) either with the gasification line 34 (when present), or with the filling line 35.

The invention makes it possible to fill containers which are still hot and therefore deformable without them undergoing irreversible deformations, due to the limitation of the pressure differential which it allows between the inside and the outside of the containers. In addition, it has been found that the filling liquid contributes to cooling the bottom. containers, before the external pressure is brought back to ambient level. As a result, the bottoms are stabilized when the external pressure is released.

Of course, and as follows from the above, the invention is not limited to those of the embodiments and applications which have been more particularly envisaged: on the contrary, it embraces all variants.

Claims

1. Method for avoiding irreversible deformation or deterioration of a plastic container (8; 22; 220; ... 225) comprising at least one zone whose temperature exceeds the softening temperature of the material, during a filling operation comprising a phase during which a significant pressure difference appears between the interior of the container and the environment outside the filling installation, characterized in that, at least during part of said phase, as long as '' it is not thermally stabilized and is still deformable, the container is placed in an enclosure

(9; 23B, 23H; 230B, 230H; ...; 235B, 235H) seals the insulation of the external environment, and the pressure inside the enclosure is modified in relation to the external environment of so as to reduce, or even cancel, the pressure difference between the inside and the outside of the container.

2. Method according to claim 1, characterized in that the pressure difference between the interior of the container and the external environment is obtained by creating a vacuum (17) in the container, and the pressure inside the enclosure is modified by reducing it (18) to bring it closer to or even reach that of the interior of the container.

3. Method according to claim 1, characterized in that the filling being carried out with a product, such as a liquid, carbonated, and consequently comprising a prior phase of pressurization (12) internal of the container with the gas used for gasification , the modification of the pressure inside the enclosure is carried out by injecting (13) a pressurized fluid into one enclosure.

4. Method according to claim 3, characterized in that the fluid is a gas.

5. Method according to claim 4, characterized in that the gas injected into the enclosure is the same as that used for gasification inside the container.

6. Method according to claim 4, characterized in that the gas injected into the container is different from that injected into the enclosure.

7. Method according to claim 6, characterized in that the gas is compressed air.

8. Method according to one of claims 1 to 7, characterized in that the pressure change in the enclosure and the pressure change in the container take place simultaneously.

9. Method according to claim 2, characterized in that the pressure reduction in the enclosure is initiated before that in the container.

10. Method according to one of claims 3 to 7, characterized in that the pressure change in the enclosure to put it in overpressure is initiated after that in the container.

11. Application of the method according to one of claims 1 to 10 for filling plastic containers obtained by heating, then blowing, alternately drawing / blowing, of preforms, immediately after blowing, alternately drawing / blowing.

12. Installation for implementing the method according to one of claims 1 to 10, characterized in that it has at least one enclosure (9; 23B, 23H; 230B, 230H; ...; 235B, 235H) waterproof to receive at least one container (8; 22; 220; ...; 225), means for placing the interior of the container in communication with a filling duct (14; 21; 35; 350; ...; 355), and means to change the pressure inside the enclosure and inside the container.

13. Installation according to claim 12, characterized in that the means for modifying the pressure inside an enclosure consist of a duct (37) putting the enclosure in communication with means for reducing (18) the pressure inside the enclosure, and the means for modifying the pressure in the container, consist of a conduit (38) putting the container in communication with means for reducing (17) the pressure inside the container.

14. Installation according to claim 13 characterized in that the conduits (37; 38) associated with an enclosure are connected together and with a single means, such as a vacuum pump, for reducing the pressure in the enclosure and in the recipient.

15. Installation according to claim 14 characterized in that the conduits (37; 38) associated with an enclosure are connected to separate means, such as vacuum pumps, to reduce the pressure in the enclosure and in the container.

16. Installation according to claim 12, characterized in that the means for modifying the pressure inside an enclosure consist of a conduit

(36, 360; ...; 365) putting the enclosure in communication with means for increasing (13) the internal pressure, and the means for modifying the pressure in the container are constituted by a conduit (34; 340; ...; 345) putting the container in communication with means for increasing (12) the internal pressure.

17. Installation according to claim 16, characterized in that the conduits (36; 360; ...; 365; 34; 340; ...; 345) associated with an enclosure are connected to each other and to a single source of fluid to increase the pressure in the enclosure and in the container.

18. Installation according to claim 17, characterized in that the filling product being gasified, the single source of fluid is the source of production of the gasification gas.

19. Installation according to claim 16, characterized in that the conduits (36; 360; ...; 365; 34; 340; ...; 345) associated with the same enclosure are associated with separate sources of fluid to increase the pressure in the enclosure and in the container.

20. Installation according to one of claims 12 to

19, characterized in that each enclosure has two parts separable from each other, an upper part (23H;

230H; ...; 235H) forming a cover associated with the head

(30; 300; ...; 305) for filling and a lower part (23B; 230B; ...; 235B) forming a receptacle for receiving the container (22; 220; ...; 225).

21. Installation according to claim 20, characterized in that it comprises means (28; 250; ...; 255; 260; ...; 265; 290; ...; 295) for bringing each lid closer or apart. of the corresponding receptacle.

22. Installation according to claim 21, characterized in that it comprises means (24) for supporting the upper parts and the lower parts, while allowing the approximation of an upper part relative to the corresponding lower part, and for driving said parts over a determined route (27).

23. Installation according to claim 21, characterized in that the means (24) for supporting and for driving an enclosure are a carousel rotating around an axis (31), and the means for bringing the upper and lower parts together are constituted by a cam (28) fixed relative to the installation, said cam cooperating with at least one roller (290; ...; 295) associated with a rod (250; ...; 255) for supporting and guiding one of the parts of the enclosure.

24. Installation according to claim 23, characterized in that the rod supports the lower part (230B; ...; 235B) of the enclosure.