EP0029039A1

EP0029039A1 - Flexible wall container for pressurized products.

Info

Publication number: EP0029039A1
Application number: EP80900924A
Authority: EP
Inventors: Alain Buquet
Original assignee: Thimonnier SAS; Societe de Conditionnement en Aluminium SCAL GP SA
Current assignee: Thimonnier SAS; Societe de Conditionnement en Aluminium SCAL GP SA
Priority date: 1979-05-23
Filing date: 1980-12-01
Publication date: 1981-05-27
Also published as: DE3063073D1; IT8022122A1; IT8022122A0; AR223525A1; ATE3268T1; IT1193934B; ES250878Y; BR8008691A; ES250878U; ZA803071B; FR2457223A1; BE883431A; WO1980002544A1; FR2457223B1; GR67668B; JPS56500567A; EP0029039B1

Abstract

L'invention concerne l'industrie des emballages, plus particulierement la fabrication de recipients a paroi souple et mince pour des liquides sous pression. La particularite de ces recipients est d'avoir au moins un fond en forme de calotte bombee (1) solidaire d'une collerette cylindrique (8) coaxiale s'etendant de part et d'autre de la calotte (1). Cette collerette (8) renforce la resistance du fond tout en assurant sa bonne liaison avec le corps. Ces recipients permettront le conditionnement dans des conditions economiques de liquides sous pression tels que les boissons carbonatees.The invention relates to the packaging industry, more particularly the manufacture of flexible and thin-walled containers for liquids under pressure. The particularity of these containers is to have at least one bottom in the form of a domed cap (1) integral with a coaxial cylindrical collar (8) extending on either side of the cap (1). This collar (8) reinforces the resistance of the bottom while ensuring its good connection with the body. These containers will allow the packaging under economical conditions of pressurized liquids such as carbonated drinks.

Description

FLEXIBLE APAROIS CONTAINER FOR PRODUCTS UNDER PRESSURE AND METHOD FOR PRODUCING SUCH A CONTAINER

The present invention relates to the production of flexible-walled containers intended to contain pressurized products such as beer or carbonate liquids. More particularly, it relates to the production of flexible material bottoms for these containers.

Containers with flexible walls can be made from light and inexpensive materials, such as paper, plastic, metallic foil, or thin laminate complexes combining the qualities of various materials. These containers are economical. They also have the advantage of being much less dangerous than rigid containers if they are used as projectiles when they are full. Therefore, we recommend their use, during public events, for the distribution of drinks or various objects.

After use, these containers are easily crushed. As waste, they have reduced volumes that are easy to handle.

Given these very diverse qualities, the use of these containers has been widely developed for the packaging of products such as milk and various pressurized drinks or chemicals.

However, for pressurized products, their use has scarcely spread so far. This is due to the fact that, so that flexible containers do not deform and tear under internal pressure, they must be given, from their manufacture, their form of natural equilibrium under pressure, that is to say a shape approaching that of the sphere, or at least a cylindrical shape with a circular section closed by two bottoms in the form of domed caps. However, if the realization of bodies of cylindrical containers resistant to pressure poses little problem, the production of domed bottoms and, above all, the method of connecting these bottoms with the body have proven to be difficult problems. In addition, for storage and handling, and even use, domed bottom containers are not very practical. It is desirable to extend the body of the containers at least on one side by a skirt ending in a flat section. This skirt, preferably rigid, has the dual role of protecting the bottom in the shape of a domed cap and give the container a seat, allowing it to stand upright.

The flexible walls are generally made of laminated materials with a core or at least an internal reinforcement which ensures mechanical resistance while appropriate coatings provide on each face the functions of resistance to corrosion or abrasion. The core of these flexible walls is often a thin sheet of aluminum which performs the functions of sealing and tensile strength but which has poor corrosion resistance. This core is protected on the internal side of the container by a coating which must be inert with respect to the content, and even aseptic if this content is a food or pharmaceutical product. The coatings of the internal faces of the body as well as of the bottoms must meet the same requirements. They are, most often, identical, or at least in very similar composition materials. They can therefore easily be glued or welded to each other.

In the majority of cases, the slightest contact between the product contained and the core of one or other of the walls would cause corrosion with degradation of the wall and pollution of the product. Given the thinness and complexity of the flexible laminated walls, butt welding of these walls with connection of the various layers is not industrially possible. The welding of the walls by overlap is also not admissible because it would let the section of one of the walls appear raw inside. For the wall whose edge would appear inside, the core would come into contact with the product, which cannot be accepted.

For the longitudinal weld of the cylindrical body, the edge of the internal plastic coating can be crushed to make it cover by creep the metal edge as proposed in French patents 1,440,935 and 1,571,778. However, for the circular weld between the domed bottom and body, especially for the welding of the second bottom closing the container, the crushing of the plastic coating would not be regular enough. This technique is practically not applicable. In addition, it would lead to an additional operation to fix in the extension of the body a cylindrical skirt which houses the domed portion in the form of a cap of the bottom and which allows the container to stand. We can also fold out the edge of one of the walls and glue or weld the second wall overlapping the first. As shown in FR 1 359 243 and CE 361 188, so that the fold does not risk opening under tension, the covering exceeds the width of the fold and the second wall is welded or glued beyond the excess thickness of the fold. For this, the second wall must be pushed against the first beyond this extra thickness. This technique commonly used for longitudinal welds is hardly feasible for the circumferential welding of a body on a bottom, in particular for the welding of the second bottom when the interior of the container has become inaccessible and that it is, the more often, filled with the product to be packaged.

As another solution proposed for the production of receptacles with flexible walls, we know those given by the patents US 3,712,497 and FR 2,311,730. These patents propose to use funds with a section in the general shape of M. The central part of these bottoms are in the form of a domed or frustoconical cap. The edge of this cap is turned outward to form an annular groove with a concavity turned towards the top of the cap, ie towards the outside of the container. This annular groove is extended by a cylindrical skirt whose diametrical section corresponds to the two legs of the M.

It can be seen in the drawings of these patents that the external face of the collar is in the extension and of the same material as the internal face of the cap. This external face of the flange can thus stick or weld without difficulty on the internal face of the body.

This M-shaped bottom form seems to solve the contradictory problems posed by pressure and corrosion. There remains, however, a difficult problem of resistance to pressure along the connection line of the body and bottom surfaces, as described in FR 2 311 730.

The pressure forces which are exerted on the entire surface of the bottom, in particular on the annular groove, have, in fact, an axial resistance which pushes the bottom by tending to progressively unwind the annular groove towards the outside. In addition, the body connection area with the upturned edge of the cap forms an acute dihedral inside which exerts internal pressure which tends to open the dihedral and to progressively spread the flexible walls opposite. For the connection between bottom and body to resist, it is essential to distribute the pressure force over a certain extent of the facing wall surfaces to relieve the weld at their connection line.

FR 2 311 730 gives a solution which consists in stiffening by an annular element added the connection groove between the domed cap of the bottom and its turned edge. However, this solution is expensive. It involves consumption of additional material corresponding to the manufacture of the rigid annular element. It requires an additional operation of placing the rigid element, an operation which can hardly be done at the current production and filling rates of the packaging.

The object of the present invention is to provide a better solution to the problem of producing containers with flexible walls resistant to pressure, in particular to the production of the bottom edges and of their connection with the body.

This solution consists, as in the last solution, in making a bottom in the shape of a domed cap bordered by a coaxial cylindrical collar. But, instead of the collar being composed only of an edge turned outward towards the top of the cap, it develops on either side of the plane defined by the periphery of the domed cap. The axial section of the bottom and its flange thus has a shape substantially in H and no longer in M. The section of the cap corresponds to the horizontal bar of H while the section of the cylindrical flange forms the two vertical bars, and on the other side of the cap.

The collar thus comprises two substantially symmetrical elements:

- a first element in the form of a thin cylindrical lip which extends the edge - of the domed cap with which it is tangentially connected.

- a second cylindrical element with the same axis and the same diameter which extends the lip but in the opposite direction. This second element corresponds to the edge returned from the flexible bottoms of the prior art with an M section, it surrounds and shelters the domed portion of the cap.

This flange in two elements is connected tangentially with the periphery of the cap without inflection point. It considerably regidifies the bottom and makes any reinforcement element such as that proposed by FR 2 311 730 useless.

In the most frequent case, the bottom in laminated sheet is produced from a blank in the shape of a glove finger composed of a cap and a cylindrical skirt extending the periphery of the cap. This cap is turned over by pushing it inside the skirt. We also return a skirt portion adjacent to the cap which comes inside the lower part of this skirt. The base of the skirt is possibly flared to form a side flange. The various operations for forming the bottom from a laminated sheet blank can be carried out practically simultaneously on double-acting presses operating at rapid rate.

Thus, after turning, there is, starting from the axis, a cap which continues with a cylindrical portion of skirt in the extension of the periphery of the cap. This first portion of the skirt is that which has been turned on itself inside the second part. The wall then continues with the second unreturned portion of the skirt. It surrounds the inverted part, extending in the opposite direction to the direction of the cap beyond the plane of its periphery.

The coating protecting the internal face of the cap thus continues without any solution of continuity on the external face of the collar, this thanks to the rolling up of the skirt. If the internal coating of the cap is identical or at least very similar to that of the body, the same is true for the external coating of the collar which is similar to the internal coating of the body. As in the case of the two patents US 3,712,497 and FR 2,311,730, the connection between the flange and the body by welding or gluing over the entire height of the flange poses no problem. To have maximum adhesion, the diameters of the cap and its flange are chosen so that the flange fits right into the body of the container undergoing a very slight contraction which applies the opposite surfaces against each other. The H-shaped bottom formed by the cap and its protective flange forms a cartridge that is easy to install in the cylindrical body.

In the part where, by rolling up on itself, the skirt forms a double-walled lip, the opposite faces of the skirt are linked to one another by means such as welding or gluing. This operation freezes the relative dimensions of the bottom, that is to say the height of the collar relative to the cap. This operation is generally done at the same time as the connection between the flange and the body of the container.

The invention will be better understood from the following description of a particular example illustrated by the accompanying drawings.

Figure 1 shows in axial section a blank in the form of a thimble with a cylindrical skirt.

Figure 2 shows in axial section the bottom after deformation of the flange, by inversion of the domed cap and part of the skirt of the glove finger.

Figure 3 shows in axial section the bottom permanently fixed inside a container body by its flange.

Figure 4 shows in axial section a similar bottom, also fixed inside a container body. The base of the collar is flared in the form of a flange.

Figure 5 shows in axial section a container closed by two bottoms according to the invention.

Figure 6 shows, in section perpendicular to the axis, the wall of the body at the longitudinal joint.

Figures 7 and 8 show in plan and in section a bottom with an easy opening device by glued lid. The blank in the thermowell of FIG. 1 consists of a domed cap 1 and a cylindrical skirt 2 which extends around the periphery 3 of the domed cap. The domed cap has an arrow "f" and an outside diameter "d". The length "1" of the skirt 2 is greater than the arrow "f" of the cap 1.

The thimble blank shown in FIG. 1 has a core 4 of aluminum sheet 0.14 mm thick. This sheet is protected against corrosion on each side by a layer of polyethylene. The polyethylene layer 5, which must be in contact with the product, inside the container, as shown in Figures 3 or 4, has a thickness of 80 microns. The layer 6 which must protect the aluminum against the atmosphere has a thickness of 30 microns. This blank J_ was itself obtained by stamping a flat blank, not shown.

At this stage of manufacture, it can be seen in FIG. 1 that the internal layer 5 is present outside the blank as a thermowell, while the layer 6 is inside.

As represents in. Figure 2: _r the cap 1 of the thimble and a first part of the skirt 2_ are turned over. The apex 7_ of the domed cap is pressed towards the base plane P of the skirt, with a depth f + h close to but slightly less, however, by a height e. We have gift born then in the blank its final domed cap shape bordered by a flange 8 of height h + f + e which extends on either side of the periphery 3 of the flange.

Here, h = 6 mm, e = 3 mm, f = 11 mm, d = 55 mm.

The bottom section, as shown in FIG. 2, has an H shape, the two vertical bars of which consist of the section of the collar 8 while the rounded bottom 1 'corresponds to the horizontal bar. We can consider that the cylindrical collar 8 _^ consists of two elements: an upper lip 9 formed by a double wall thickness, of height h in the extension of the periphery 3 of the domed cap 1 'and a lower element 10 substantially similarly diameter d. This element 10 corresponds to the turned edge of US Patents 3,712,497 and FR 2,311,730, while the upper lip 9 provides by itself sufficient rigidity which makes an additional reinforcing element unnecessary as in the French patent.

For a better understanding, the upper lip 9 has been shown with a large thickness, whereas this thickness is in fact only of the order of 0.50 mm, the two wall thicknesses being applied one against each other.

A bottom was thus produced, the domed cap 1 'of which is housed in a sort of cylindrical cartridge of diameter substantially d, of thickness ε relatively thin, and of height h + f + e. This cartridge just enters the body 11 of the container with even a slight tightening of the order of 0.2 mm on the diameter. The lower element 10 of the collar 8 allows precise positioning of the curved portion with respect to the body 11, as shown in FIG. 3. It usefully reinforces the end of this body 11.

It can be seen that the internal layer 5 of the domed portion of the bottom continues without a solution of continuity outside of the flange 8 and is located opposite the internal layer 12 of the body. The layers 5 and 12 of the bottom and of the body are here both made of polyethylene. They can be glued or welded without difficulty. The very slight tightening of the collar 8 in the body 11 is sufficient to ensure good contact of the facing surfaces over the entire height of the collar.

After the bottom has been placed in the body, the flange 8 is welded over its entire height to the internal layer 12 of the body, ie over the height h + f + e. Simultaneously, the layer 6 is welded onto itself over the height h corresponding to the lip 9 obtained by inversion of the skirt part adjacent to the domed cap 1a. Thus, the collar 8 is immobilized with respect to the cylindrical body 11 and the domed cap 1 'with respect to the collar 8. This double welding is easily carried out by heating the aluminum layers by high frequency induction.

When the container is full, the force exerted axially by the internal pressure p on the end 13 of the lip 9 is minimal due to the small thickness of this lip of the order of 0.50 mm. The connection groove made of flexible material between the flange 8 and the domed cap 1 ′ does not have an appreciable surface oriented perpendicular to the pressure forces p in the axial direction and which is liable to gradually deform as is the case in US 3,712 497 and FR 2 311 730. The two walls of the thin lip 9 are substantially contiguous, closely linked by a weld zone 14. The external face of the lip 9 is itself linked to the body by the weld 15 over the entire height. h, here 6 mm. The three concentric walls form a block over the entire height h. Finally, it should be added that, if the internal pressure p exerts an axial force on the end of the lip 9, ie on a crown of width 0.50 mm and diameter d, this same internal pressure exerts in p ' radial which applies the lip 9 against the wall of the body 11, this according to a cylinder of height h, here 6 mm. There is no effort to detach the lip 9 relative to the wall of the body. For a better understanding, the weld zones 14 and 15 are shown considerably enlarged. They are actually extremely thin, the facing surfaces being pressed against each other and welded without adding material.

The axial force absorbed by the domed cap 1 ′ of diameter d_ is transmitted by the edge 3 in the form of a tangential tensile force over the whole of the lip 9. It does not apply, as in the art front, on the single connection line 16 between lip 9 and internal layer 12 of the wall 11, but is distributed over the entire height surface h of the welds 14 and 15. Finally, the lower element 10 of the flange is itself even welded to the wall 11. It helps to block the upper lip 9 by preventing any possibility of displacement by sliding of this lip against the wall 11. This lower element 10 reinforces the end of the cylindrical wall 11 which is the part of the container most exposed to shocks.

To facilitate the positioning of the base while further strengthening the edge of the container, it is possible to use funds, the flange 8 of which is flared at its base in the form of a lateral flange 17, as shown in FIG. 4.

To facilitate installation and welding of the bottom in the body, one can give the collar 8 a very slightly conical shape, tapering towards the center of the container.

The internal surface of the cylindrical body 11 must not have any asperites of appreciable thickness. When the cylindrical body is obtained by winding a rectangular sheet of laminated complex, overlap welds of the types described in FR 1 359 243 or FR 1 571 771 are not used. The sheet is wound so that its two ends are presented end to end as shown in FIG. 6. The mechanical resistance along the longitudinal joint is ensured by welding or gluing of a resistant tape 18 to the outside of the container, while the sealing and the internal protection against corrosion are ensured by the application of a thin strip 19 of flexible material. This ribbon, for example a "Saranex" ribbon from DOW CHEMICAL has a moisture-impermeable barrier layer 20 of polyvinilydene chloride protected on both sides by a thin layer of polyethylene

The composite sheet constituting the body 11 represented in FIG. 6 is constituted like the bottoms of an internal protective layer 12 of polyethylene, of an aluminum sheet 21 and of an external layer 22 of polyethylene. However, to increase the rigidity of the container, this sheet 11 also comprises a layer of cardboard 23 with a thickness of the order of 0.4 mm.

The external resistant tape 18 has a width 1 of 10 mm as well as the internal sealing tape 19. The tape 18 shown is cut from the same sheet as that constituting the body. The internal tape 19, very malleable and flexible, has a thickness of 0.08 to 0.1 mm. When each bottom is put in place, it is partially pushed back into the longitudinal gap 24 between the ends which come end to end of the sheet constituting the body 11. The edges of this strip 19 are simultaneously flattened in a bevel and are connected practically without roughness with the polyethylene layer 12.

For chemically less aggressive products, such as carbonated water, an easy opening device can be produced as shown in FIGS. 7 and 8. One or more perforations 25 are before stamping in the flat blank in which the bottom must be formed. These perforations 25 are closed with a thin cover 26 which is fixed by gluing. The blank and the cover 26 are formed at the same time and the device shown in FIGS. 7 and 8 is obtained very economically.

In the example described, the surface layers for protection against corrosion and humidity, 5, 6, 12, 22 are made of polyethylene. These protective layers can be made of various other plastics or varnishes. Thus, the outer layers 6 and 22 are frequently made of varnish with a thickness of the order of 10 microns.

Claims

CLAIMS 1 / Containers with flexible walls for the packaging of products under pressure such as carbonate liquids, at least one end of which is closed by a domed cap bordered by a coaxial cylindrical collar, characterized in that the collar develops on both sides 'other of the plane defined by the periphery 3 of the domed cap 1', the axial section of the cap and its flange having substantially an H shape.

2 / container according to claim 1, the bottom of which is made of laminated sheet, characterized in that the flange comprises a first element in the form of a thin cylindrical lip 9 with a double wall, constituted by a skirt first extending the edge 3 of the cap convex 1 ', then rolled up on itself towards the outside to extend beyond the plane of the periphery 3 and form the second element 10 of the collar, this second element surrounding and protecting the domed cap 1'.

3 / container according to claim 2, characterized in that the facing surfaces of the skirt are linked to each other in the area where, by rolling up, the skirt forms the lip 9 extending the edge 3 of the domed cap.

4 / A container according to any one of claims 1, 2 or 3, icaractérisé in that the top 7 is slightly recessed and sheltered inside the lower portion 10 of the collar of height h + f + e.

5 / A container according to any one of claims 1, 2, 3 or 4, characterized in that the flange 8 is flared at its base in the form of a lateral flange 17.

6 / container according to any one of claims 1, 2, 3, 4 or 5, characterized in that the body 11 is obtained by winding a sheet whose two ends are end to end, a strong tape 18 glued on the outside along the longitudinal joint ensuring its mechanical strength and a thin tape 1 9 glued on the inside ensuring the tightness of this joint. 7 / container according to any one of claims 1, 2, 3, 4, 5 or 6, characterized in that it comprises an easy opening device produced by at least one perforation 25 of one of the bottoms, then sealing with a glued cap 26.

8 / A method of producing a container according to any one of claims 2, 3, 4, 5, 6 or 7, characterized in that the bottom is formed by first forming a blank thimble which the crown 7 of the domed cap 1 is turned over as well as a first portion of the skirt in the direction of the base plane P of the thermowell, which the bottom is introduced with its flange 8 thus formed inside of a cylindrical body 11 to form the bottom and that the outer layer 5 of the flange 8 is bonded to the internal surface 12 of the cylindrical body 11 at the same time as the skirt surfaces facing each other in the area where they form by rolling up a lip 9 in extension of the periphery 3 of the domed cap 1 '.