EP1587664A1

EP1587664A1 - Method and installation for the production of a plastic container

Info

Publication number: EP1587664A1
Application number: EP03815416A
Authority: EP
Inventors: Gérard Emmer
Original assignee: Sidel SA
Current assignee: Sidel SA
Priority date: 2002-12-23
Filing date: 2003-12-17
Publication date: 2005-10-26
Also published as: FR2848906B1; WO2004065105A1; AU2003300640A1; US20060097417A1; KR20050088465A; FR2848906A1; CN1744982A; JP2006511380A

Abstract

The invention relates to a method and installation for the production of a plastic container (1). The inventive method comprises: (i) a step involving the thermal conditioning of at least some areas (2) of a preform (3) of the container, such that the temperature of said areas exceeds the glass transition temperature of the constituent material thereof; and (ii) a step involving the injection of a fluid into the preform (3) so as to cause the preform to expand in order to shape same into a container. According to the invention, unrestrained expansion of the above-mentioned areas of the preform is performed, i.e. without a mould, by controlling at least one injection parameter of the fluid in order to obtain the definitive container (1).

Description

METHOD AND INSTALLATION FOR MANUFACTURING A CONTAINER IN PLASTIC MATERIAL.

The subject of the invention is improvements to the methods and installations for manufacturing plastic containers from pre-injected preforms which are thermally conditioned and then transformed into containers during an expansion carried out by injecting a fluid inside. of the preform. It applies to the manufacture, at lower cost, of containers intended more particularly, although not exclusively, to receive contents whose price is low (for example, without this being limiting, water or other refreshing liquids) relative to that of the containers.

In recent years, the manufacture of plastic containers from pre-injected preforms has experienced considerable growth, in particular thanks to the use of polyethylene terephthalate (P. E.T.). In the meantime, other materials have been envisaged and / or used with more or less success such as, by way of nonlimiting examples, polyethylene naphthalate (PE N.), Polypropylene (PP), or mixtures or overlays of various materials.

To manufacture a container with such materials, the preform, which is in the form of a test tube formed in an injection mold, is introduced into a thermal conditioning unit, also called an oven, in which its constituent material is reheated in order to be brought to a temperature higher than its glass transition temperature, however without reaching its crystallization temperature. At the end of this thermal conditioning phase, the preform is transferred to a mold belonging to a blowing unit or, more frequently, to a mold belonging to a stretch-blowing unit. The mold includes a cavity with an imprint of the final container. When the unit is a blowing unit, the preform, after having been introduced into the mold, is subjected there to an injection of fluid, generally air, at high pressure, typically of the order of 40 bars. , to be transformed into a final container. When the unit is a stretch blow molding unit, which is the most frequent case, the preform, after being introduced into the mold there is subjected to a stretching along its longitudinal axis, generally accompanied by an injection of pre-blowing fluid (under a pressure of ten bars) and an injection of blowing fluid. The use of a high blowing pressure allows perfect control of the shape and details of the final container, since the material can be pressed into the smallest gaps in the mold. Then, either the container is stored, empty, before being transported to a filling unit, or it is directly transferred along a more or less direct route to a filling unit, in which it is filled, then it is then capped. .

In general, the thermal conditioning unit is arranged so that the neck of the preform is not heated. Indeed, the neck is a part of the preform, which corresponds to the neck of the final container. It is therefore produced in its final shape and dimensions during the injection of the preform and must not be deformed in the subsequent blowing or stretch-blowing phases. The neck comprises an opening (the neck proper) and a peripheral zone thereof with means (thread, rim, or the like) suitable for receiving the closure member (stopper, capsule or other) of the final container. In addition, it comprises, in most cases, means, typically a flange, for transporting the preform and the container after its production, and / or after its filling and / or other manipulations.

Generally, the thermal conditioning unit is arranged to allow differentiated heating of certain areas of the preform, in order to optimize the distribution of the material in the final container. The preform heating profile is determined taking into account the dimensions and shape of the preform, as well as the dimensions and shape of the final container. Thus, for example, document FR-A-2 703 944 in the name of the applicant discloses a process and a device for selective or preferential heating of certain areas of the preform to result in a bottle.

The known devices and methods for manufacturing containers by blow molding or stretch blow molding have drawbacks.

On the one hand, the molds, which constitute important elements to allow the final conformation of the containers and the repeatability of the forms are expensive. Indeed, they require delicate machining and finishing operations (polishing) of the cavities which they comprise. The machines known to the applicant comprise from two to forty molds, some being single-cavity, others two-cavity. The means for compressing the blowing fluid, in order to reach the high pressures necessary for taking shape in the cavities, are also costly elements and all the more complex the higher the flow rate which is required of them. It should be noted that some machines produce 60,000 containers per hour, which assumes that the compression means are able to deliver approximately 240,000 liters of fluid per hour (assuming that the containers, blown at 40 bars, have a volume of 1 litre).

Setting the blowing (or stretching and blowing) parameters so that the containers produced are correct is a complex operation.

However, it has been found that, for certain markets, the known methods and devices for blowing or stretch-blowing were not entirely suitable, in particular because of their complexity and their cost. The invention aims to remedy these drawbacks.

According to the invention, a method of manufacturing a plastic container, of the type consisting in thermally conditioning at least certain zones of a preform of the container so that the temperature of said zones exceeds the glass transition temperature of their material component, and to inject a fluid into the preform to cause its expansion in order to conform it into a container, is characterized in that it consists in carrying out a free expansion, that is to say without the presence of a mold , at least some of said areas of the preform, and to control at least one parameter for injecting the fluid to reach the final container.

The invention is very particularly advantageous because it can be implemented without requiring high injection pressures. Thus, tests have made it possible to produce containers with a fluid pressure of less than 10 bars. Also, the invention allows it to overcome the need for expensive compressors; moreover, it allows to implement a machine structure Alleg _u ed in comparison with known machines puisque- they require a design suitable for high pressures used. By heating preforms with a standard heating profile, such as a profile for obtaining bottles on known machines, the method of the invention makes it possible to obtain containers whose general shape is that of an elongated bubble. Such a general form, which has limited possibilities of declination of form, is however particularly suitable, for example for the packaging of liquids, such as still water anywhere on the planet, in particular in markets where the the appearance of the container is not essential.

In one implementation, a limited number of injection parameters are controlled, which makes it possible to obtain containers in the form of an elongated bubble with an indeterminate although sufficiently significant volume.

However, this is not a problem since one can very well envisage in such a case a sale by weight of the filled container.

Furthermore, from identical preforms, it is possible to obtain containers of different volumes: it suffices for this to modify at least one of the fluid injection parameters. This advantage is particularly advantageous to exploit in places such as emerging markets where it is difficult to ensure the manufacture or supply of a wide variety of preforms.

According to another characteristic, the method consists in controlling at least one fluid injection parameter so that the final internal volume of the container is within a predetermined range with respect to a reference volume.

According to another characteristic, the method consists in controlling at least one parameter for injecting the fluid, taking into account the temperature of said zones of the preform.

According to other characteristics: a controlled parameter is the pressure of the fluid injected inside the preform; a controlled parameter is the flow rate of the fluid injected inside the preform. According to another characteristic, the pressure is variable during the injection; in an implementation, it consists in starting the injection with a pressure higher than that in. end of injection, and the initial pressure and flow of fluid are controlled to prevent the material of the preform, therefore that of the container, from freezing before obtaining the desired expansion, and the pressure at the end of injection is reduced to prevent material from bursting.

According to another characteristic, a controlled parameter is the temperature of the fluid. According to another characteristic, the parameters of injection of the fluid are controlled so that the stopping of the expansion is naturally caused by freezing of the material constituting the preform when the expansion becomes significant, so that when the material is frozen the reaction forces exerted by the material oppose those exerted by the fluid; in a variant, the parameters of injection of the fluid are controlled so that the stopping of the expansion is naturally caused by freezing of the material constituting the preform when the expansion is such that the final internal volume of the container is included in a predetermined range with respect to a reference volume, so that when the material is frozen the reaction forces exerted by the material oppose those exerted by the fluid.

According to other characteristics: it consists in stopping the injection of fluid after a predetermined time; the fluid is introduced into a capacity prior to its injection and transferred into the preform in order to cause its expansion; the fluid is a gas; the container being intended to be filled with a liquid after its manufacture, it consists: firstly in causing the preform to expand using a gas, then, while maintaining a pressure residual gas inside the container when it is formed, immediately fill the container with a liquid subjected to a gas pressure at least equivalent to the residual pressure in the container.

According to another characteristic, the fluid is a liquid; in one implementation, the container being intended to be filled with a liquid, it consists in using said liquid to cause the expansion of the preform in order to conform it into a container, during the filling phase of the container which thus constitutes its manufacturing phase; in one implementation, it consists in introducing into a capacity a volume of liquid corresponding to that desired in the container, and in predetermining injection parameters of said liquid to allow that all of the liquid contained in said capacity is introduced into the preform during its expansion in order to reach the final container.

This characteristic is particularly advantageous, since the formation and filling of the container are carried out in a single step.

According to another characteristic, to vary the shape of the containers from one manufacture to another, it consists in modifying the heating profile of said zones of container preforms during their thermal conditioning.

Thus, the invention is therefore not limited to obtaining containers having an elementary shape of elongated bubble, but it allows, to a certain extent, to obtain variations around this shape.

Thus, for example, by creating a heating profile with more or less cold zones, it favors the displacement of certain zones of the preform during the injection of the fluid, which allows to a certain extent to control the shape of the container. final. By linking this control of the heating profile with that of the parameters, it becomes possible to control the shape and volume of the containers.

According to another characteristic, a container manufacturing installation comprising a thermal conditioning unit for at least certain areas of a preform and an expansion unit with at least one device for expanding said preform, which device for expanding is associated with a source of fluid to cause the expansion of the preform by injection of said fluid, and comprises means for sealingly insulating the interior of the preform from the outside environment, and means for communicating the interior of the preform with said source of fluid for causing the expansion of the preform, is characterized in that the expansion unit is a free expansion unit of at least some of said areas of the preform, and comprises means for controlling at least one parameter for injecting the fluid in order to control the expansion of the preform with a view to arriving at the final container. Other characteristics and advantages of the invention will appear on reading the description of the figures below which illustrate respectively:

- Figure 1, a front view of a thermally conditioned preform relatively homogeneously and a corresponding container that it is possible to obtain by implementing the method of the invention;

- Figure 2, a view schematically illustrating a preform with a non-homogeneous heating profile and a corresponding container that it is possible to obtain by implementing the method of the invention;

- Figure 3, a block diagram of an annex device for conforming the bottom of the containers obtained by the implementation of the invention; - Figure 4, a block diagram of a variant of the device of Figure 3; Figure 5, a block diagram of a container manufacturing installation according to the invention;

- Figures 6 to 1 1, various variants of fluid injection systems which may be contained in the installation of Figure 3.

FIG. 1 shows a first type of container 1 which the invention makes it possible to obtain, by carrying out a free expansion of the body 2 of a preform 3, thermally conditioned according to a relatively homogeneous heating profile, above of the glass transition temperature of the material making up the preform 3. For PET, the heating profile must be such that the temperature of the body 2 is around 120 ° C. By homogeneous profile, it is meant without abrupt temperature variation from one zone to another of the body of the preform.

The container 1 of FIG. 1 has a body 4, in the general shape of an elongated bubble, which body 4 of the container T is obtained from the material constituting the body 2 of the preform 3. The container 1 also has a neck 5 of same as a collar 6 marking the limit between the collar

5 and the body 4, and, in a manner known per se, the neck 5 and the collar 6 of the container 1 are elements which are present on the preform 3 and are not modified during the formation of the container 1. To this end, the neck 5 and the collar 6 of the preform 3 are not heated during thermal conditioning, or are very slightly heated. The thermal conditioning process implemented to obtain such a container 1 with a body 4 in the form of an elongated bubble can be perfectly conventional: it can consist, for example, of passing the preform in front of an appropriate radiation source, such as an assembly infrared radiation lamps and reflectors, by rotating it about its longitudinal axis. For this purpose, it is possible to use a thermal conditioning unit operating according to the principle set out in FIG. 1 of the document FR-A-2 703 944 mentioned above.

The invention is not limited to the production of containers in the form of an elongated bubble. Thus, in Figure 2, there is shown a second type of container 7 which it is possible to obtain. The container 7 has a biobobed body, with three parts, one upper 8, the other lower 9, and a central part 10 with an average diameter smaller than that of parts 8, 9, and separating the latter. This container 7 can be obtained by heating various annular zones of a preform 1 1 differently: a central annular zone 1 2 of the preform 1 1 is heated to a temperature lower than that of the other upper annular zones 1 3 and lower 14. I this results in greater difficulty in stretching the material of the central annular zone 1 2 of the preform 1 1, so that the container 7 ultimately has the central part 1 0 with an average diameter smaller than that of the parts 8, 9, which central part 1 0 is formed with the material of the central annular zone 12 of the preform 1 1, and the upper 8 and lower parts 9 of the container are made respectively with the material of the upper annular zones 1 3 and lower 14 of the preform 1 1. As in the case of FIG. 1, the preform 1 1 and the container 7 also have a neck 1 5 and a collar 1 6.

An implementation device making it possible to obtain such a container 7 may comprise, for differently heating various zones of the preform, a conditioning unit with radiation lamps infrared and facing reflectors, such as that which appears in FIG. 1 of the document FR-A-2 703 944 mentioned above. With such a unit, in order to heat the central annular zone 12 less than the upper 13 and lower 14 zones of the preform, it suffices for example to apply less power to the lamps opposite the zone 12 of the preform. It is also possible to implement the variant illustrated with reference to FIG. 1 3 of the same document FR-A- 2 703 944, that is to say employing reflectors with non-reflecting zones opposite the central annular zone 1 2. A heating method as described above makes it possible to obtain containers in the form of a bilobed bubble in which each section perpendicular to the longitudinal axis of the container is substantially circular.

Of course, the number of lobes could be greater than two, by adapting the heating profiles.

It is also possible to obtain containers which are no longer bilobed, but in the form of an elongated bubble, in which all or part of the sections perpendicular to the longitudinal axis of the containers would be non-circular, in particular ovoid, for example by using one or other of the variants of FIGS. 4 to 1 1 of document FR-A-2 703 944; finally, it would still be possible to combine circular sections with non-circular sections and / or to incorporate lobes, themselves of circular section or not, for example by appropriately combining the various modes of thermal conditioning described above. . It is also easily understood that if, in accordance with the invention, one plays on the parameters of injection of the fluid, it is entirely possible to control, to a certain extent, the expansion of the preform, therefore the final volume of the container. Among the controllable parameters are the fluid pressure, its flow rate, its temperature and the total volume of injected fluid.

To control the final volume of the container, the total volume of injected fluid can be controlled differently, depending on whether this fluid is a liquid or a gas: for example, when the fluid is a liquid, it is possible to fill a capacity with a volume of fluid 40 corresponding to the volume of the container to be obtained, and then to empty the capacity in the preform to cause its expansion; it is also possible to inject liquid directly into the preform while measuring the quantity injected, for example using a flow meter, then to stop the injection after a time such that the volume injected corresponds to the desired volume; when the liquid is a gas, knowledge of the pressure, flow rate and injection time makes it possible to calculate the volume of the container.

However, one must take into account the conditions in which the preform leaves the conditioning unit: the higher the temperature of its body, the easier it is to cause expansion. Thus, if we consider two identical preforms heated according to similar profiles, but at different temperatures, and into which a fluid is injected under identical predetermined conditions, then they will reach a given volume in different times, the warmer preform being transformed faster. As a corollary, for two identical preforms heated, one can reach a given volume before the other, for example if the flow rate and / or the pressure and / or the temperature of the injected fluid is (are) higher . It is perfectly understandable that the final volume of the container will be all the closer to a reference volume when all the parameters mentioned will be taken into account.

Furthermore, to predetermine the parameters, it must be taken into account that, as and as it expands, the material constituting the preform tends to cool and to freeze so that the material becomes less and less malleable. It is therefore necessary to adapt the parameters so that the material is not frozen before a sufficient volume is reached.

However, in view of a distribution "by weight" of the content, the control of the parameters can be simplified. I t is entirely conceivable to simply inject the fluid with a pressure or a determined flow taking into account the temperature • of the preform and / or that of the fluid, such that, for sure, the preform undergoes an expansion, and to let the material freeze naturally: thus, it is certain that a container with an acceptable volume will be obtained. It is still possible to fine-tune the parameters so that, for sure, the volume final internal container is within a predetermined range with respect to a reference volume, while allowing the material to "freeze naturally."

As already indicated, the method of the invention makes it possible to obtain containers in the form of an elongated bubble or containers with lobes, that is to say, more generally, containers with rounded shapes.

Consequently, such containers do not have a seating area, such as a bottom, allowing them to stand upright.

It is however possible to provide a seating area on such containers, during a step subsequent to their formation, by causing a support between the container area at the location where the seating area is to be produced and an external bearing surface.

Said step can be carried out by using one or the other of the devices illustrated by way of examples in FIGS. 3 or 4. In FIG. 3, the seating area 1 7 of a container 1 8 is centered around the longitudinal axis 1 9 of the container 1 8. It is produced by causing a support, against an element 20, of the zone 21 of the end of the container, that is to say the zone which is centered around said longitudinal axis 1 9 and which has an outward convexity (visible on the left-hand side of FIG. 3) before the formation of the seating area. Under the effect of the pressure exerted when the element 20 is pressed, the end zone 21 turns over, as visible on the right part of FIG. 3, so that a zone appears at this location. 22 with a concavity facing outwards, the periphery of this area 22 constituting the seating area 1 7.

The support is obtained by causing a relative approximation between the container 1 8 and the element 20, which is illustrated by the double arrow 23.

In the example illustrated in this FIG. 3, the element 20 has a flat bearing surface. In the variant of Figure 4, the realization of a zone 1 7 sitting on a container 1 8 is obtained by using a member 24 which has a bearing surface with a protrusion 25, to favor the reversal of the zone of the container where the bearing surface 1 7 is to be made. Thus, in the example of FIG. 4, the protuberance 25 is of frustoconical shape. Furthermore, as illustrated in FIG. 4, it is possible to produce the support zone 17 in an offset manner relative to the longitudinal axis 1 9 of the container 1 8.

Of course, it is possible to use either the device of FIG. 3 or that of FIG. 4 to produce seating areas 17 centered around the longitudinal axis 1 9 of the receptacles 1 8 or offset from this axis longitudinal 1 9 of container 1 8.

It has been found that the production of a seating area 17 is facilitated when it is carried out on an open container, but which is, at least partially, filled with liquid. The reaction exerted by the mass of the liquid facilitates the inversion and the shaping of the seating area.

The member 20 or 24 for producing the seating areas can be associated with the container filling machine. However, in this case, to avoid loss of liquid during the formation of said zones, it is desirable to take into account the reduction in the internal volume of the container which occurs during the inversion of the support zone.

This can be taken into account in various ways: thus, in the implementation which is illustrated in FIG. 3, the container, previously filled to a standard level 26 compared to conventional filling techniques, is maintained during the formation of the support zone under the filling head 27, which is arranged so that, during the formation of the support zone, the liquid which is in excess due to the reduction in internal volume can start again (arrow 28) through the filling head. This implementation is particularly advantageous since it is independent both of the initial volume (when it is still in the form of a bubble) and of the final volume (after formation of the seating area) of the container.

In a variant, not shown, the container is initially filled with a lower volume of liquid, as account is taken of the reduction in internal volume; in a variant, an oversized free volume is left, and a leveling is carried out after the formation of the seating area. Other variants, within the reach of those skilled in the art, are conceivable, in particular, that which consists in making the bottom out of the filling machine.

The block diagram of an installation for implementing the invention appears in FIG. 5. In principle, the installation is conventional, that is to say that it includes a unit 29 for thermal conditioning of the preforms 30, associated with a unit 31 for the expansion of the preforms.

In the example, the thermal conditioning unit 29 is constituted in a known manner. It includes heating elements with lamps 32 and reflectors 33, for example formed in accordance with FIG. 1 of document FR-A-2 703 944, and / or one or other of its variants of FIGS. 4 to 1 1, and / or to that of FIG. 1 3. Furthermore, preferably, the thermal conditioning unit 29 includes means for protecting the neck of the preforms 30 (not visible in the figure) to prevent the necks from heating up. The thermal conditioning unit 29 also includes a device 34 for driving the preforms, such as an endless chain provided with individual members 35 suitable for transporting and each driving a preform supported by its neck between the lamps and the reflectors. The individual members 35 of the device 34 are moreover arranged so that, when they travel, the preforms 30 are rotated on themselves to allow correct reheating of the periphery of their body.

The expansion unit 31 comprises a fluid injection system, with at least one head 36 for injecting the fluid, which is connected by a conduit 37 to an assembly 38 for supplying the fluid and controlling its injection. . More detailed block diagrams of various variants of the injection system are shown in Figures 6 to 11.

Preferably, as this appears in FIG. 5, the expansion unit 31 comprises several injection heads 36 which are arranged, for example, on a rotating structure (carousel) materialized by the arrow 39, and which are each connected by a respective conduit 37 to the assembly 38 for supplying the fluid and for controlling its injection. This arrangement makes it possible to reach high production rates for containers The head or each head 36 for injection is arranged to be associated with a preform during the step of -.onformation container, ^'that is to say during the injection of fluid, and isolating, so sealed, the interior of the preform of the external atmosphere during this step, so as to prevent the fluid supplied by the respective conduit 37 in the preform via the head from escaping towards the outside during of his injection.

Preferably, means for controlling the temperature of the preforms, such as sensors (not shown) are arranged in the installation in order to provide real information at this temperature to the assembly 38 for supplying the fluid and controlling its injection, so that, if necessary, this temperature can be taken into account by said assembly 38, in order to control the injection.

The operation of the device is as follows: the preforms 30 are successively introduced (arrow 40) into the thermal conditioning unit 29, where they are individually gripped by a member 35 and they are driven, in the direction of arrows 4, 42 at through reheating elements 32, 33. At the end of their journey in the conditioning unit 29, they are unloaded individually, then taken up and transferred (arrow 43) by a transfer device, not shown, to the unit 31 expansion.

More specifically, each preform 30 is placed, in a sealed manner, opposite a head 36 of the expansion unit, and fluid is injected under predetermined conditions inside, in order to form the containers 44 which are then discharged (arrow 45) from the installation.

The expansion of the preforms has been schematically represented in this FIG. 5: there is a progressive increase in the diameter of the object (initially preform 30, then container 44) associated with the injection heads 36. In FIGS. 6 and 7, two variants of a fluid injection system are illustrated with an assembly 38 for supplying the fluid under pressure and for controlling its injection. These two variants, which have a minimal difference between them, each allow the use of gas or liquid as expansion fluid; they also allow a control of all or part of the parameters (flow rate and / or pressure and / or quantity and / or time and / or temperature of the fluid relative to that of the preform).

The fluid injection system illustrated in these Figures 6 and 7 comprises three injection heads 361, 362, 363 associated with the assembly 38 for supplying the fluid and controlling its injection. It is understood that the number of heads could be different.

Each head 361, 362, 363 is associated with a respective valve 461, 462, 463 with remote opening and closing control (such as an electric or pneumatic control). The remote control of the valves is carried out from a unit 47 for managing the operation of the injection system. In the example, this unit 47 is shown as an integral part of the assembly 38 for supplying the fluid and controlling its injection. Each valve can be all-or-nothing (single flow) or proportional (variable flow) control.

Each valve 461, 462, 463 is also interposed between its respective associated head 361, 362, 363 and a conduit 48 for supplying pressurized fluid. The three assemblies each consisting of a valve and the respective associated head are therefore mounted in parallel on the conduit 48, so that, when a valve is open, in response to the appropriate command from the management unit 47, of the fluid can travel in the direction of the respective associated head.

In the example illustrated, a head 361 is free, while a preform 30 is disposed under the head 362, ready to be transformed into a container, and a container 44 formed is under the head 363, ready to be removed.

The difference between the variants of FIGS. 6 and 7 resides in the fact that, in the system of FIG. 6, the pressurization of the fluid is carried out outside the assembly 38 (therefore for example next to or at some distance from the expansion unit 31 of FIG. 5) and the conduit 48 for supplying pressurized fluid is a conduit entering the assembly 38, while, in the system of FIG. 7, the pressurization of the fluid is carried out inside the assembly 38 (therefore for example inside the expansion unit 31 of FIG. 5) and the duct 48 for supplying pressurized fluid is a duct internal to the '' together 38. The pressurization is carried out using a pressurizing device 49 suitable for the fluid used (compressor, booster pump, pump, etc.), which device 49 is preferably connected to the management unit 47 : thus, it is possible to act on the pressure and / or the flow leaving this device 49. In the example of FIG. 6, the device 49 for pressurization, external to the assembly 38, is supplied by a conduit 50 also external, and discharges the fluid towards the conduit 48. In the example of FIG. 7, the device 49 for pressurizing, is internal to the assembly 38; it delivers the fluid to the conduit 48 and is supplied by a conduit 50 entering the assembly 38.

The variants of FIGS. 6 and 7 make it possible to use, as fluid for causing the expansion, the liquid intended to serve as final content for the container. In particular, the use of a fluid is very particularly possible in the case of hot filling of containers (temperature close to the glass transition temperature of the preform material), since the temperature of the liquid prevents too rapid freezing of matter.

These variants also make it possible to use a gas, such as compressed air, for expansion in the unit 31, and to transfer the containers, after expansion, to a filling machine, of the filling type for still drinks. Alternatively, it is possible to provide additional respective conduits terminating in each head and to arrange the fluid supply circuits (expansion gas and filling liquid) so that, after expansion, the filling liquid can be directly supplied in the containers held under the expansion heads which are also used for filling. However, if the liquid is brought to atmospheric pressure (filling by gravity), the containers must first be degassed to balance the pressure in the container with the outside, otherwise filling remains impossible as long as the pressure in the container exceeds atmospheric pressure, but wait for the material to freeze, keeping the container under pressure for a sufficient time: in fact, if the container is degassed too quickly, before the material is frozen, the risk exists that the material will shrink and let the volume decrease. Such a training and filling cycle is therefore long. FIG. 8 presents an arrangement which makes it possible to cause the expansion of the preforms with a gas and to fill the containers immediately after expansion, without waiting for the material to freeze, so that the cycle of formation and filling of a container can be optimized. This arrangement comprises means for causing the preform to expand using a gas, means for maintaining a residual pressure of gas inside the container when the latter is formed, and means for immediately filling the container using a liquid subjected to a gas pressure at least equivalent to the residual pressure in the container. Thus, maintaining a residual pressure in the container prevents shrinkage of the material; subjecting the liquid to a gas pressure at least equivalent (therefore greater than or equal) to the residual pressure in the container allows filling by gravity, since the internal pressure of the container does not prevent the arrival of the liquid.

Advantageously, the arrangement of FIG. 8 uses the principle and the arrangements implemented in the fillers for carbonated or carbonated drinks, by taking advantage of the gasification or carbonation phase of the container, prior to its filling, to cause expansion.

To this end, the injection system of FIG. 8, illustrated in the example for the distribution of fluid in the direction of two heads 364, 365, comprises an assembly 38 for supplying the fluid under pressure and for controlling its injection. comprising a tank 51 in which there is liquid 52, surmounted by a free space 53 with gas under pressure. The gas can be compressed air or any other gas, in particular a gas useful for conditioning the liquid (carbon dioxide in the case where the liquid is a carbonated drink for example). The free space 53 of the top of the tank 51 is placed in communication with a device 490 suitable for carrying out the pressurization and / or maintenance of the gas pressure inside this free space 53. Depending on the case , the device 490 can for example be a compressor or a device for supplying the gas useful for conditioning the liquid. The liquid 52 is brought into the tank 51 by a conduit 54 provided with a non-return mechanism 55, to prevent the gas under pressure in the tank from escaping.

To bring the gas contained in the free space 53 from the top of the tank 51 to the heads 364, 365, this free space 53 is moreover placed in communication with the heads 364, 365, by means of respective conduits 564, 565, in each of which is interposed a valve 464, 465 with remote opening and closing control. The remote control of the valves is carried out from a unit 47 for managing the operation of the injection system. Each valve can be all-or-nothing (single flow) or proportional (variable flow) control.

Thus, by opening the valve associated with a head, gas contained in the free space 53 at the top of the tank 51 is directed towards the corresponding head.

To bring the liquid into the containers, the bottom of the tank 51 is placed in communication with the heads 364, 365, thanks to. respective conduits 574, 575 in each of which is inserted another valve

584, 585 with remote opening and closing control. These valves can also be single or variable flow.

Thus, by opening the valve associated with a head, the liquid contained in the tank 51 goes to the corresponding head.

The opening and closing control, both of the valves 464, 465 for supplying gas into the heads and those 584, 585 for supplying the liquid are provided by a unit 47 for managing the operation of the injection system; the management unit is also connected to the device 490 suitable for carrying out the pressurization and / or maintenance of the gas pressure inside the free space 53 of the tank 51.

The operation of the device is as follows. When no preform is present under the heads 364, 365, the valves 464, 465 for supplying gas to the heads and those 584, 585 for supplying the liquid are placed in the closed position by the management unit 47 the operation of the injection system. After a thermally conditioned preform has been placed under a head 364, the valve 464 corresponding for the gas supply is opened by the management unit 47, gt the expansion of the preform is caused. Then, when -Texpansion is finished, the corresponding valve 584 for supplying the liquid is open, so that the liquid arrives by gravity into the container. In known manner, the filling must be accompanied by an evacuation of the gas contained in the container. However, to avoid shrinking of the material, in particular at the start of the filling phase, it is necessary that the evacuation occurs without the pressure in the container falling too much; Similarly, when the liquid must maintain a certain pressure (carbonated or carbonated drink), the pressure in the container should not decrease too much during the evacuation accompanying the filling. Furthermore, it is preferable that the evacuation does not disturb the arrival of liquid, and is carried out by a circuit separate from that of liquid arrival. To this end, in one implementation, the evacuation is carried out directly towards the tank, by the air intake circuit itself, so that the overall pressure of the fluid circuit incorporating the tank and the container does not change not during filling, and only fluid transfers (gas, then liquid) are carried out at constant pressure, which also makes it possible to maintain a suitable gas pressure in the container, if necessary. In this case, at the time of opening of the valve 584 for supplying liquid, the valve 464 for the gas inlet is not closed by the management unit 47, and the two valves are only closed again. after completion of filling. In a variant, not shown, the evacuation is carried out directly towards the tank, however by a dedicated circuit, which may include gas filtration means.

I t is however conceivable to start filling by evacuating the gas towards the tank and to finish it by evacuating the gas towards the outside (return to atmospheric pressure), to further reduce the duration of the filling cycle: in fact, the filling liquid, when it is brought to a temperature below the glass transition temperature of the material constituting the container, contributes to freeze the material when it enters the container. Therefore, after the filling has started and the material has become frozen, it becomes possible to reduce the pressure in the container to the level of the external pressure. This is however only possible with flat liquids (water or other) which do not require the maintenance of a gas pressure after filling. It is easily understood that, with the arrangements described with reference to FIGS. 6 to 8, in order to more or less precisely control the final volume of a container, the management unit 47 must more or less precisely control the following injection parameters of the fluid (gas or liquid) used to cause the expansion, also taking into account the temperature of the preform at the time when it is brought under a head (or even the temperature of the preform at the outlet of the unit 29 packaging visible in Figure 5): fluid temperature and / or injection pressure and / or flow rate and / or injection time. In fact, for example, at identical injection pressure and flow rate, two identical preforms heated will not reach the same volume in equivalent time, if the fluid injected into one is at a temperature different from the fluid injected into the other ; similarly, at identical pressure and flow rate and injection temperature, two differently heated preforms will not reach the same volume in equivalent time; what is more, in certain cases, it will be impossible for the two preforms to reach the same volume, the material of one of them being able to solidify during the injection. It is therefore necessary that suitable sensors are placed in the installation. To this end, according to the number of parameters that it will be chosen to control, the device management unit 47 of FIGS. 6 to 8 may incorporate devices (not shown) which allow this unit to manage all or part of the various mentioned parameters (flow rate, pressure, temperature of the preforms and / or of the fluid, duration) implemented during the injection.

However, in order to facilitate the control operations, in a preferred implementation of the invention, the device of FIG. 9 is used, which makes it possible to reduce the number of parameters to be checked, and which is moreover usable for carrying out containers of different volumes.

This device comprises a cylinder 59 - piston 60 assembly, which determines a chamber constituting a capacity 61 of variable volume, in function of the position of the piston 60 in the cylinder 59. The capacity is connected by a conduit 62 to a source of fluid, not shown

A second conduit 63 connects the capacity to a head 366 for injecting fluid. On this second conduit, a valve 466 with remote opening and closing control is interposed between the head 366 and the capacity.

A non-return valve 64 is disposed on the conduit 62 between the source of fluid and the capacity.

The operation of the device is as follows: the piston 60 is placed in a determined position in the cylinder 59, so that the capacity 61 has an initial volume; then fluid (liquid or gas) is introduced (arrow 620) into the capacity 61 through the conduit 62, so as to fill it; the valve 466 is open and the piston 60 is pushed by its actuating rod 65, so as to reduce the volume of the capacity and to inject the fluid towards the head 366. The non-return valve 64 opposes the return of the fluid towards the source.

It is well understood that, if the fluid used is incompressible (liquid for example), and that the driving speed of the piston is chosen so that the entire volume of fluid can be removed before the material freezes, which speed d The drive is determined by focusing the equipment, then the volume of the container is predetermined by the initial volume of the capacity. Consequently, it is possible to constitute series of containers of identical volumes, or of containers each of predetermined volume.

It is also conceivable that, if the fluid is compressible and the driving speed of the piston is chosen so that the entire volume of fluid can be removed before the material freezes, the final volume of the container will depend not only on the volume initial capacity, but also the initial pressure and temperatures of the fluid and the material of the preform. These various parameters must therefore be taken into account when trying to predetermine the final volume of the containers.

In Figure 1 0 is illustrated a first alternative embodiment of the device of Figure 9, a fluid injection system with an assembly 38 for supplying the fluid under pressure and for controlling its injection. The system, shown here for feeding two heads 367, 368, comprises on the one hand a conduit 66 for supplying the fluid to the assembly 38, two devices conforming to that of FIG. 9, which are connected in parallel to the conduit 66, and a management unit 47, for controlling the system. Thus, each device conforming to that of FIG. 9 comprises a non-return valve 647, 648 between the conduit 66 and its respective capacity 617, 618, and a valve 467, 468 with remote opening and closing control interposed between the head 367, 368 and the capacity 61 7, 61 8 respectively. The management unit 47 makes it possible to control the valves 467, 468 and the motor members of the rods 657, 658 for actuating the pistons associated with each capacity, in order to obtain suitable flow rates and / or pressures, taking account of the case if necessary, the temperature of the fluid and the temperature of the preforms, using appropriate sensors, not shown.

The device of Figure 1 0 allows to use either gas or liquid as injection fluid.

In Figure 1 1 is illustrated an improved variant of the invention, which implements the device of Figure 9 on a system similar to that of Figure 8, so that the same elements have the same references.

The only differences between the arrangements of the systems of Figures 8 and 1 1 are as follows: first, in each of the conduits 564, 565 connecting the free space 53 of the top of the tank 51 to the heads 364, 365, upstream of the valve 464, 465 with remote opening and closing control, a respective capacity 614, 61 5, constituted by a cylinder-piston assembly, has been inserted; also another valve

644, 645 with remote opening and closing control is positioned upstream of the respective capacity, therefore between the free space 53 of the top of the tank 51 and the respective capacity, which valve 644,

645, is substituted for the non-return valve of figure 9.

The remote control of all of the valves is connected to a unit 47 for managing the operation of the injection system; so are even the driving members of the rods 654, 655 for actuating the pistons associated with each capacity.

Such an arrangement makes it possible to obtain a high efficiency, since this capacity 61 4, 61 5, is initially filled with an initial volume of gas under pressure, corresponding to that of the gas contained in the free space 53 of the top of the tank 51 , and the movement of the piston to transfer the gas to the respective associated head 364, 365 increases the pressure.

The operation of the system, for example to supply the head 364, is as follows:

- initially, at least the valves 584, 585 for supplying liquid and 464, 465 for supplying air are put in the closed position by the management unit 47;

- The piston is positioned in the chamber to determine a capacity 61 4 of predetermined volume (taking into account the temperatures of the fluid, and / or the material, and the desired final volume); and gas contained in the free space 53 of the top of the tank 51, enters the capacity 614, through the valve 644 which is open;

- this valve 644 is closed; the valve 464 interposed between the capacity 614 and the corresponding head 364 is opened, and the piston is pushed (actuator 654) so as to reduce the volume of the capacity and entrain the fluid in the container, to cause its expansion.

Then, when the expansion is complete, the corresponding valve 584 for supplying the liquid is open, so that the liquid arrives by gravity into the container.

The filling cycle corresponds to that of FIG. 8. As mentioned with reference to FIG. 8, the filling must be accompanied by an evacuation of the gas contained in the container without the pressure in the container falling too much and without it disturbing the arrival of liquid. As in the case of FIG. 8, the evacuation can be carried out directly towards the tank, by the air intake circuit itself, so that the overall pressure of the fluid circuit incorporating the tank and the container does not change not during filling. To allow this, at the time of opening of the valve 584 for supplying liquid, not only the valve 464 for the gas inlet is not closed by the management unit 47, but the valve 644 upstream of the capacity is again open, to allow the gas to leave towards the free space 53 from the top of the tank 51. After completion of the filling, the filling valve 584 is closed, as is the valve 464 located between the capacity 614 and the head 364; the piston is again positioned in the chamber to determine a capacity 61 4 of predetermined volume, which capacity is filled with gas coming from the free space 53 from the top of the tank 51, and the cycle begins again.

It is easily understood that with all the variants illustrated, it is perfectly possible to control the flow rate and / or the pressure of the injected fluid, either by appropriately controlling the devices for pressurizing the fluid used, corresponding to the devices 49 (visible in Figures 6 and 7), 490 (visible in Figures 8 and 1 0), either by moving more or less quickly, thanks to their driving members, the rods 65, 654, 655, 657, 658 (visible in the figures 9, 1 0, 1 1) actuation of the pistons associated with the capacities, either by appropriately piloting the device 490 for pressurizing the fluid used, visible in FIG. 1 0, and by moving more or less quickly, thanks to their driving members, the rods 654, 655 (visible in FIG. 1 1)) for actuating the pistons associated with the respective capacities 614, 61 5.

Thus, it is particularly advantageous to start the injection with a flow rate and / or a pressure higher than that at the end of injection, and to control the initial pressure and / or flow rate of fluid to prevent the material constituting the preform, therefore that of the container, does not freeze before obtaining the desired expansion, and reducing the pressure, therefore the flow rate at the end of injection to prevent the material from bursting. Of course, the invention is not limited to the embodiments described and specifically claimed; it embraces all the equivalents within the reach of those skilled in the art.

Claims

claims

1. Method for manufacturing a container (1; 7; 1 8; 44) of plastic material, of the type consisting in thermally conditioning (29) at least certain zones (2; 12; 1 3; 14) of a preform (3 ; 1 1; 30) of the container so that the temperature of said zones exceeds the glass transition temperature of their constituent material, and to inject a fluid into the preform to cause its expansion in order to form it into a container, characterized in that it consists in carrying out a free expansion (at 31), that is to say outside of the presence of a mold, of said zones of the preform, and in controlling at least one parameter of injection of the fluid to result in final container.

2. Method according to claim 1, characterized in that it consists in controlling at least one fluid injection parameter so that the final internal volume of the container is within a predetermined range relative to a reference volume.

3. Method according to one of claims 1 or 2, characterized in that it consists in controlling at least one fluid injection parameter taking into account the temperature of said areas of the preform.

4. Method according to one of claims 1 to 3, characterized in that a controlled parameter is the pressure of the fluid injected inside the preform.

5. Method according to one of claims 1 to 3, characterized in that a controlled parameter is the flow rate of the fluid injected inside the preform.

6. Method according to claim 4, characterized in that the fluid pressure is variable during the injection.

7. Method according to claim 6, characterized in that it consists in starting the injection with a flow rate and / or a pressure greater than that at the end of injection, and in that q ue the flow rate and / or the initial pressure of fluid is controlled to prevent the material of the preform, and therefore that of the container, from freezing before obtaining expansion desired, and the flow and / or pressure at the end of injection is reduced to prevent the material from bursting.

8. Method according to one of claims 1 to 3, characterized in that a controlled parameter is the temperature of the fluid.

9. Method according to claim 1, characterized in that it consists in controlling the parameters of injection of the fluid so that the stopping of the expansion is naturally caused by freezing of the material constituting the preform when the expansion becomes significant, so that, when the material is frozen, the reaction forces exerted by the material oppose those exerted by the fluid.

10. Method according to claim 2, characterized in that it consists in controlling the parameters of injection of the fluid so that the stopping of the expansion is naturally caused by freezing of the material constituting the preform when the expansion is such that the final internal volume of the container is within a predetermined range with respect to a reference volume, so that when the material is frozen the reaction forces exerted by the material oppose those exerted by the fluid.

1 1. Method according to one of claims 1 to 3, characterized in that it consists in stopping the injection of fluid after a predetermined time.

1 2. Method according to one of claims 1 to 1 1, characterized in that the fluid is a gas.

13. Method according to claim 12, characterized in that, the container being intended to be filled with a liquid (52) after its manufacture, it consists:

- initially to cause the expansion of the preform;

- then, while maintaining a residual gas pressure inside the container when the latter is formed, immediately filling the container with a liquid subjected to a gas pressure at least equivalent to the residual pressure in the container.

14. Method according to claim 1 3, characterized in that it consists firstly in sealingly insulating the interior of the preform of the external atmosphere; to put the interior of the preform into communication with a gas source (490, 53) for the filling of the filling liquid, in order to cause the expansion of the preform using, said source; then, when the expansion is complete, while maintaining the insulation with the outside and the communication between the inside of the preform with the gas source, causing the filling (584, 585) of the container thus formed with the liquid under pressure.

15. Method according to one of claims 12 to 14, characterized in that the gas is compressed air.

1 6. Method according to one of claims 1 to 1 1, characterized in that the fluid is a liquid.

1 7. Method according to claim 1 6, characterized in that the container being intended to be filled with a liquid, it consists in using said liquid to cause the expansion of the preform in order to conform it into a container , during the filling phase of the container which thus constitutes its manufacturing phase (Figure 6, Figure 7).

1 8. A method according to claim 1 7, characterized in that the liquid is hot.

1 9. Method according to one of the preceding claims, characterized in that it consists in introducing into a capacity a predetermined volume of fluid, in sealing communication the capacity with the preform, and in transferring fluid from the capacity to the preform, by controlling at least one transfer parameter of said fluid outside of the capacity to allow the expansion of the preform and its transformation into a container (Figure 9, Figure 1 0).

20. Method according to one of the preceding claims, characterized in that to vary the shape of the containers from one manufacture to another, it consists in modifying the heating profile of said zones (12; 13; 14) of container preforms during their thermal conditioning.

21. Method according to one of the preceding claims, characterized in that it comprises the step of producing a seating area (1 7) on the container, during a step following expansion, by causing a support (20) between the container area at the location where the seating area is to be performed and an external support surface.

22. Installation for manufacturing containers comprising a unit (29) for thermal conditioning of at least one preform and an expansion unit (31) with at least one expansion device (36; 361; ...; 368) of said at least one preform, which expansion device is associated with a source of fluid (50; 54; 62; 66) to cause expansion of the preform by injection of said fluid, and comprises means for isolating, so sealed, the interior of the preform of the external environment, and means (461; ...; 468) for communicating the interior of the preform with said source of fluid to cause the expansion of the preform, characterized in that the expansion unit is an expansion unit free from at least some of said areas of the preform, and comprises a management unit (47) for controlling at least one parameter of injection of the fluid so to control the expansion of the preform with a view to arriving at the def initif.

23. Installation according to claim 22, characterized in that it comprises the management unit (47) is associated with means for measuring a temperature of at least one zone of the preform, and the means for controlling at least a fluid injection parameter are arranged to perform this control according to the result of the preform temperature measurement.

24. Installation according to claim 22, characterized in that the management unit (47) is associated with means for controlling the pressure of the fluid injected inside the preform.

25. I nstallation according to claim 24, characterized in that the means for controlling the pressure of the fluid injected inside the preform are arranged to vary the pressure of the fluid during injection.

26. Installation according to claim 22, characterized in that the management unit (47) is associated with means for controlling the flow rate of the fluid injected inside the preform.

27. Installation according to claim 22, characterized in that the management unit (47) is associated with means for controlling the temperature of the fluid.

28. Installation according to claim 22, characterized in that the management unit (47) is associated with means for controlling the duration of injection of the fluid.

29. I nstallation according to claim 22, characterized in that, the container being intended to be filled with a liquid after its manufacture, and the fluid used for expansion being a gas (53), it comprises means for maintaining a residual pressure of gas inside the container when the latter is formed, and for immediately filling the container with a liquid subjected to a gas pressure at least equivalent to the residual pressure in the recipient.

30. Installation according to claim 29, characterized in that it comprises a reservoir (51) of pressurized filling liquid, a gas source (490) for pressurizing the reservoir, and means (464, 465; 644, 645) to put the interior of the preform into communication with said source of pressurized gas, in order to cause the expansion of the preform using said source and means for, when the expansion is completed , maintain the insulation with the outside and the communication between the inside of the preform and the gas source, and cause the filling of the container thus formed.

31. I nstallation according to claim 22, characterized in that the container being intended to be filled with a liquid supplied by a filling unit, the expansion unit is constituted by the filling unit and the management unit (47) is associated with means (49, 697, 698) for controlling the pressure of the filling liquid.

32. Installation according to one of claims 22 to 31, characterized in that the source of fluid for causing the expansion consists of a capacity (61, 614, 61 5, 617, 61 8) containing a volume of fluid at less equivalent to that desired in the final container, and the management unit (47) is associated with means (65, 654, 655, 657, 658) for transferring the fluid contained in the capacity to the preform and with means to control at least one transfer parameter of said fluid outside capacity to allow the final container to have a predetermined volume.

33. I nstallation according to claim 22, characterized in that the unit (29) of thermal conditioning comprises means for preselecting the profile the preform heating profile.