Deformable container without air return

Abstract

The present invention relates to a container (10) comprising: - an elastically deformable outer receptacle (12), and - a flexible, sealed inner layer (26) defining a storage space (28) for the product to be dispensed and being configured to retract as the product is dispensed, - a dispensing device (30) comprising a first one-way valve (34) and a support (32) defining an accommodating recess for accommodating the first one-way valve (34), the first one-way valve (34) comprising: - an elastically deformable flexible membrane, - a sealing seat accommodated in a fastening cavity of the accommodating recess, a dispensing cavity of the accommodating recess comprising indentations suitable for allowing the passage of the product in a dispensing state of the first one-way valve (34).

Description

[0001] DEFORMABLE CONTAINER WITHOUT AIR RETURN

[0002] Description

[0003] Technical field of the invention

[0004] The present invention relates generally to an airless container designed to contain a liquid or pasty product and associated with a dispensing device without air return.

[0005] Technical background

[0006] An airless container is one that contains a product that is not in contact with atmospheric air. This type of container is advantageous in that it allows the product to be preserved for longer after the container has been opened, without the need to add preservatives to the product composition, and also limits product contamination.

[0007] Furthermore, airless containers are advantageous in that they allow viscous products to be dispensed efficiently, unlike “atmospheric” containers, which require a certain degree of fluidity for the product to flow along the walls.

[0008] The currently known airless containers comprise rigid containers fitted with an airless pump that comprises a dosing chamber and can be actuated by a push-button. When the pump is actuated by the push-button, the product in the dosing chamber is delivered to the dispensing hole. In particular, the pump sucks the product from the airless container by means of a vacuum created in the dispensing member in order to transfer a volume of product from the container into the dosing chamber of the pump as the push-button rises.

[0009] However, airless containers, while effective, have the drawback of being time-consuming and complex to assemble, due to the large number of parts required.

[0010] In addition, the use of a pump entails the use of different materials such as plastic, steel and glass, complicating the subsequent recycling thereof.

[0011] Finally, this type of airless container associated with a pump limits the possible shapes for the container due to the structure of the pump. Specifically, most airless containers are piston systems, the main constraint of which is their cylindrical shape in order to ensure a good seal for the assembly.

[0012] There is therefore a need for an airless container that is simple to manufacture and assemble with fewer parts, which is easily recyclable and user- friendly, and can take a variety of shapes.

[0013] Summary of the invention

[0014] The invention provides a container for holding and dispensing a liquid or pasty product comprising: an outer receptacle which comprises an outer side wall, an outer bottom and an inner surface which defines an internal space of the outer receptacle, said outer receptacle being elastically deformable as a result of pressure exerted on said outer side wall, and a flexible, sealed inner layer extending inside the internal space of the outer receptacle, the flexible inner layer defining a storage space for the product to be dispensed, and the flexible inner layer being configured to retract as the product is dispensed, a product dispensing device mounted on an upper end of the outer receptacle, the dispensing device comprising a support and a first one-way valve, the support defining an accommodating recess for accommodating the first one-way valve, extended by a product outlet hole for the product from the storage space, the first one-way valve comprising: an elastically deformable flexible membrane held at its center by a fastening stud, said flexible membrane comprising an upper face and a lower face, a sealing seat accommodated in a fastening cavity of the accommodating recess and sealingly fastened in the fastening cavity, the sealing seat comprising a receiver into which the fastening stud is fitted, a free end of said flexible membrane cooperating with said sealing seat of said first one-way valve in a closed state of the first one-way valve and so that said flexible membrane can detach from said sealing seat when the first one-way valve is in a dispensing state, a dispensing cavity of the accommodating recess extending between the fastening cavity and the outlet hole, the dispensing cavity being defined by a main wall of the support and comprising indentations suitable for allowing the passage of the product in the dispensing state of the first one-way valve.

[0015] According to other features of the invention: the dispensing cavity comprises a hemisphere shape defined by the main wall of the support; the fastening cavity of the accommodating recess is defined by a cylindrical wall of the support which extends from the main wall of the support and into the internal space of the outer receptacle; the indentations are separated from one another by contact surfaces formed on the main wall in the dispensing cavity so that the free end of the flexible membrane slides against the contact surfaces when it is detached from the sealing seat; the indentations extend substantially from a base of the hemisphere-shaped dispensing cavity to substantially a top of the dispensing cavity; the flexible inner layer is configured to delaminate from the inner surface of the outer receptacle; the container comprises a second one-way valve installed in a foot of the container mounted on a lower end of the outer receptacle and at least covering the outer bottom, the foot defining, with the outer bottom, an interspace in fluid communication with the internal space via at least one natural opening formed in the outer bottom, the second one-way valve being configured to allow the passage of a fluid only to the interspace. Brief description of the figures

[0016] Further features and advantages of the invention will become apparent from the following detailed description, which may be understood with reference to the attached drawings in which:

[0017] [Fig.1a] is a general perspective view of a container according to one example of the invention comprising an outer receptacle and a dispensing device without air return fitted with a lid in the closed position;

[0018] [Fig .1 b] is a general perspective view of the container shown in [Fig.1a] with the lid in an open position;

[0019] [Fig.2] is an axial cross section through the container shown in [Fig.1a] showing the dispensing device fitted with a first one-way valve and a foot fitted with a second one-way valve;

[0020] [Fig.3] is a close-up cross-sectional view of the dispensing device without air return of the container shown in [Fig.1 b] comprising a support defining an accommodating recess for the first one-way valve, with the lid in its open position;

[0021] [Fig.4] is a close-up cross-sectional view of the dispensing device without air return of the container shown in [Fig.1 a] comprising the support defining the accommodating recess for the first one-way valve, with the lid in its closed position;

[0022] [Fig.5] is a close-up cross-sectional perspective view of the dispensing device without air return showing a dispensing cavity of the accommodating recess provided with indentations;

[0023] [Fig.6a] is a schematic view of the container in use when a user exerts pressure against an outer side wall of the outer receptacle of the container;

[0024] [Fig .6b] is a schematic view of the container in use when a user releases the pressure against the outer side wall of the outer receptacle of the container. Detailed description of the invention

[0025] In the following description, identical, similar or analogous elements will be referred to by the same reference numbers.

[0026] Figs. 1a and 1 b illustrate a container 10 for dispensing a liquid or pasty product such as a cream, ointment or paste, particularly for cosmetic use.

[0027] The container 10 comprises an outer receptacle 12 which comprises an outer side wall 14 and an outer bottom 16.

[0028] In particular, the outer side wall 14 extends around an axis of revolution R so as to give the outer receptacle 12 of the container 10 a cylindrical shape.

[0029] It should also be borne in mind that the outer receptacle could take any other shape without departing from the scope of the invention.

[0030] The outer receptacle 12 further comprises an inner surface 18 which defines an internal space 20 of the outer receptacle 12.

[0031] In this case, the internal space 20 is closed off at a lower end 22 of the outer receptacle 12 by the outer bottom 16.

[0032] The outer side wall 14 is elastically deformable as a result of pressure exerted on said outer side wall 14.

[0033] In other words, the outer side wall 14 is capable of deforming under the effect of mechanical pressure, for example pressure exerted by the hand of a user, and then returning to its initial, undeformed state without breaking or damage to its material when the mechanical pressure ceases, for example when the hand of the user releases the outer side wall 14.

[0034] The container 10 also comprises a flexible, sealed inner layer 26 that extends inside the internal space 20 of the outer receptacle 12. More precisely, according to the example illustrated, the flexible inner layer 26 covers the inner surface 18. The flexible inner layer 26 then defines a storage space 28 for the product to be dispensed.

[0035] According to one non-limiting example of the invention, the flexible inner layer 26 is configured so that it delaminates from the inner surface 18 of the outer receptacle 12.

[0036] In other words, the flexible inner layer 26 is configured to peel away from the inner surface 18 and then retract as the product is dispensed.

[0037] The operation of the flexible inner layer 26 will be described in detail later, when the product dispensing method is described.

[0038] The container 10 also comprises a product dispensing device 30, which can be seen in particular in Figs. 3 to 5.

[0039] In particular, the dispensing device 30 according to the invention is a dispensing device without air return.

[0040] The dispensing device 30 is mounted on the upper end 24 of the outer receptacle 12.

[0041] The dispensing device 30 comprises, inter alia, a support 32 and a first one-way dispensing valve 34.

[0042] In particular, the support 32 comprises a main wall 36 which extends in a radial plane of the outer receptacle 12, considering the axis of revolution R of the outer side wall 14.

[0043] In particular, the main wall 36 covers the internal space 20 of the outer receptacle 12.

[0044] The main wall 36 is extended peripherally by a fastening skirt 38 comprising a first fastening means 40 which is able to cooperate with a complementary second fastening means 42 formed on the outer side wall 14, at the upper end 24 of the outer receptacle 12, so as to secure the support 32 to the upper end 24 of the outer receptacle 12. According to the example illustrated, the first fastening means 40 is formed by an internal lug of the fastening skirt 38 and the second fastening means 42 is formed by a shoulder under which the first fastening means 40 is accommodated, so as to fasten the support 32 to the upper end 24 of the outer receptacle 12 by snap-fitting.

[0045] According to another non-limiting example which is not illustrated, the first and second fastening means can take the form of complementary threads.

[0046] The support 32 also comprises a product outlet hole 44 for the product from the storage space 28.

[0047] More precisely, the outlet hole 44 is formed on the main wall 36 of the support 32.

[0048] Even more precisely, the outlet hole 44 is formed at the end of a cylindrical passage 46 defined by the main wall 36 of the support 32.

[0049] As can be seen in the example in Figs. 3 and 4, the support 32 comprises a lid 48 that is pivotally mounted with respect to the main wall 36.

[0050] It should also be borne in mind that, in a non-limiting manner, the support could be without a lid without this example departing from the scope of the invention.

[0051] The lid 48 comprises a plugging projection 50 configured to cooperate in a form-fitting manner with the cylindrical passage 46 of the support 32.

[0052] In other words, the plugging projection 50 is configured to fit snugly into the cylindrical passage 46.

[0053] It is thus understood that the cooperation between the plugging projection 50 and the cylindrical passage 46 prevents the passage of product through the outlet hole 44.

[0054] Thus, and according to the non-limiting example illustrated, the lid 48 is pivotally mounted with respect to the main wall 36 by means of a pivot joint and in such a way that the lid 48 pivots between an open position in which its plugging projection 50 extends outside the cylindrical passage 46 as can be seen in [Fig.3] and a closed position in which its plugging projection 50 extends into the cylindrical passage 46 as described above.

[0055] It should also be borne in mind that, in a non-limiting manner, the lid may be without a pivot joint and could comprise any other means that allow it to be moved from the open position to the closed position without departing from the scope of the invention.

[0056] As can be seen in Figs. 3 to 5, the support 32 defines an accommodating recess 52 for accommodating the first one-way valve 34.

[0057] In particular, the accommodating recess 52 comprises a fastening cavity 54 and a dispensing cavity 56.

[0058] Thus, considering the axis of revolution R of the outer side wall 14, the fastening cavity 54 is extended axially by the dispensing cavity 56 and then by the cylindrical passage 46, at the end of which the outlet hole 44 is formed.

[0059] The first one-way valve 34 comprises a sealing seat 58 accommodated in the fastening cavity 54 of the accommodating recess 52. More particularly, the sealing seat 58 is sealingly fastened in the fastening cavity 54.

[0060] It is therefore understood that the sealing seat 58 is an insert in the fastening cavity 54.

[0061] According to the non-limiting example illustrated, the fastening cavity 54 is defined by a cylindrical wall 60 of the support 32 which extends from the main wall 36 into the internal space 20.

[0062] According to the example illustrated, the cylindrical wall extends coaxially around the axis of revolution R, and in such a way that it defines the cylindrically-shaped fastening cavity 54.

[0063] Thus, according to this example of the invention, the sealing seat 58 comprises a fastening wall 62 which extends circularly around the axis of revolution R so as to form a cylinder of complementary shape to the fastening cavity 54. Thus, according to one non-limiting example of the invention, the fastening wall 62 comprises a first fastening element for securing the sealing seat 58 in the fastening cavity 54 through cooperation with a second, complementary fastening element formed by or on the cylindrical wall 60 defining the accommodating cavity 54.

[0064] For example, the fastening wall 62 and the cylindrical wall 60 can be snap-fitted together, or else the fastening wall 62 can be force-fitted into the fastening cavity 60.

[0065] The sealing seat 58 also comprises a transverse wall 68 which extends in a radial plane considering the axis of revolution R, at an axial end of the fastening wall 62.

[0066] The first one-way valve 34 comprises an elastically deformable flexible membrane 70 held at its center by a fastening stud 72.

[0067] In addition, the transverse wall 68 comprises a receiver 74 into which the fastening stud 72 is fitted.

[0068] In the example illustrated, the receiver 74 takes the form of a through- bore in which the fastening stud 72 is mounted.

[0069] In particular, the fastening stud 72 comprises a peripheral shoulder 76 configured to form an axial stop against the transverse wall 68 when the fastening stud 72 is mounted in the receiver 74 so as to lock the fastening stud 72 in position in the receiver 74.

[0070] Fluid passages 78 are formed in the transverse wall 68, on the periphery of the receiver 74.

[0071] It is understood that the fluid passages 78 are configured to allow the product to pass from the storage space 28 to the dispensing cavity 56.

[0072] The flexible membrane 70 extends circularly around the fastening stud 72, considering the axis of revolution R.

[0073] A closed state of the first one-way valve 34, which can be seen in

[0074] Figs. 3, 4 and 5, is defined, in which it prevents the product from passing from the storage space 28 to the dispensing cavity 56, and a dispensing state of the first one-way valve 34, shown in dashed lines in [Fig.4], is defined, in which it allows the product to pass from the storage space 28 to the dispensing cavity 56.

[0075] Thus, it is understood that the flexible membrane 70 covers the fluid passages 78 in the transverse wall 68 when the first one-way valve 34 is in its closed state.

[0076] More precisely, a free end 80 of the flexible membrane 70 is configured to cooperate with the sealing seat 58 in the closed state of the first one-way valve 34.

[0077] Even more precisely, the flexible membrane 70 has a concave shape when the first one-way valve 34 is in its closed state, so as to improve contact between its free end 80 and the sealing seat 58, in particular with the transverse wall 68, to form a sealed contact between them.

[0078] In other words, the concave shape of the flexible membrane 70, together with its elastic deformation properties, provides sealed contact between the free end 80 of the flexible membrane 70 and the sealing seat 58 in the closed state of the first one-way valve 34.

[0079] An upper face 82 and a lower face 84 of the flexible membrane 70 are also defined, axially opposite one another and such that the upper face 82 extends opposite the dispensing cavity 56.

[0080] Thus, when the pressure exerted against the lower face 84 of the flexible membrane 70 is greater than that exerted against the upper face 82, the flexible membrane 70 deforms so that its free end 80 moves away from the sealing seat 58, placing the first one-way valve 34 in its dispensing state as shown in dashed lines in [Fig.4].

[0081] In other words, the detachment of the free end 80 of the flexible membrane 70 from the sealing seat 58 allows the product to pass to the dispensing cavity 56, in particular by means of the indentations 86 formed in the latter.

[0082] As can be seen in Figs. 3 to 5, the dispensing cavity 56 is in the shape of a hemisphere defined by the main wall 36 of the support 32. Additionally, the indentations 86 are formed in the dispensing cavity 56, on the main wall 36.

[0083] More precisely, the indentations 86 extend into a thickness of the main wall 36 of the support 32, into the dispensing cavity 56.

[0084] Even more precisely, the indentations 86 extend in the axial direction, considering the axis of revolution R, along the main wall 36 of the support 32, into the dispensing cavity 56.

[0085] The indentations 86 extend substantially from a base of the hemisphere-shaped dispensing cavity 56 to substantially a top of the dispensing cavity 56, close to the cylindrical passage 46.

[0086] As can be seen in Figs. 3 to 5, contact surfaces 88 formed on the main wall 36 in the dispensing cavity 56 extend between the indentations 86.

[0087] The contact surfaces 88 are shaped so that the free end 80 of the flexible membrane 70 slides against the contact surfaces 88 when it is detached from the sealing seat 58 in the dispensing state of the first one-way valve 34, as shown in dashed lines in [Fig.4].

[0088] It is thus understood that when the first one-way valve 34 transitions from its closed state to its dispensing state, the free end 80 of the flexible membrane 70 detaches from the sealing seat 58 and slides against the contact surfaces 88 at a non-zero distance from a bottom of the indentations 86 so that the product is able to move in the indentations 86 from the base of the dispensing cavity 56 to the top thereof.

[0089] It is understood then that the indentations 86 allow the product to be guided from the storage space 28 to the outlet hole 44, while controlling the amount of product dispensed.

[0090] As can be seen in [Fig.2], the container 10 comprises a foot 90 mounted on the lower end 22 of the outer receptacle 12, covering at least the outer bottom 16. The foot 90 can be secured to the lower end 22 of the outer receptacle 12 by similar means to those used to fasten the support 32 to the upper end 24 of the outer receptacle 12.

[0091] It should also be borne in mind that the attachment between the foot 90 and the lower end 22 of the outer receptacle 12 is a sealed attachment.

[0092] An interspace 92 is then formed between the outer bottom 16 and the foot 90.

[0093] Furthermore, the container 10 is configured so that the interspace 92 is in fluid communication with the internal space 20 of the outer receptacle 12.

[0094] More precisely, and according to one non-limiting example, when the outer receptacle 12 is manufactured by a co-extrusion blow-molding process, a natural opening 94 is created between the two half-disks forming the outer bottom 16, the two half-disks then not being welded together.

[0095] It should be borne in mind, however, that for the sake of clarity, the natural opening 94 created in the outer bottom 16 of the outer receptacle 12 has been depicted in Figs. 6a and 6b in an exaggerated manner in terms of its size and shape, and this should be considered only as a purely schematic representation of this natural opening 94.

[0096] The foot 90 also incorporates a second one-way valve 96 without air return, configured to allow only a fluid, in this case air, to pass into the interspace 92 during a phase of re-inflation of the outer receptacle 12, which will be described in greater detail when the product dispensing method is described.

[0097] It should also be borne in mind that the second one-way valve 96 is substantially identical to the first one-way valve 34 in terms of operation.

[0098] Thus, as with the first one-way valve 34 described above, the second one-way valve 96 comprises a flexible membrane that extends from a fastening stud and which is configured to allow or prevent fluid from passing into the interspace 92 via elastic deformation. The second one-way valve 96 also comprises a sealing seat configured to accommodate the fastening stud and which can take any shape as long as it both allows the fastening stud to be held in place and ensures a sealed connection with the flexible membrane as described above for the first one-way valve.

[0099] For example, and in a non-limiting manner, the sealing seat of the second one-way valve 96 can be formed directly by a wall of the foot 90.

[0100] The product dispensing method will now be described with reference to Figs. 1 to 6b.

[0101] The dispensing method comprises a first step in which a user pivots the lid 48 so that it goes from its closed position to its open position.

[0102] It is of course understood that in the case where the support 32 has no lid 48, this step is optional.

[0103] The user then applies pressure against the outer side wall 14 in order to deform it, as can be seen in [Fig.6a].

[0104] During this deformation of the outer side wall 14, the second one-way valve 96 located in the foot 90 of the container 10 prevents the passage of fluid at the outlet of the interspace 92, fluidically connected to the internal space 20, thereby creating an increase in pressure in the internal space 20 of the outer receptacle 12 and in the interspace 92.

[0105] It is understood that this increase in pressure in the internal space 20 and in the interspace 92 moves the first one-way valve 34 from its closed position to its dispensing position and thus allows the product to move from the storage space 28 through the fluid passages 78 in the transverse wall 68 of the sealing seat 58 to flow into the indentations 86 formed in the dispensing cavity 56, thereby guiding the product toward the outlet hole 44.

[0106] Once the user has obtained the desired amount of product, they release the pressure exerted against the outer side wall 14. As illustrated schematically in [Fig.6b], when the pressure against the outer side wall 14 is released, it returns to its initial shape due to its elastic deformation properties and a vacuum is formed in the storage space 28, causing the first one-way valve 34 to move into its closed position and thus the progressive delamination and retraction of the flexible inner layer 26.

[0107] Furthermore, when the pressure against the outer side wall 14 is released, it returns to its initial shape, generating a suction effect which opens the second one-way valve 96 to allow air to pass into the interspace 92 and then into the internal space 20 between the flexible inner layer 26 and the inner surface 18 via the natural opening 94.

[0108] Thus, it is understood that as the product is dispensed, the flexible inner layer 26 retracts in on itself.

[0109] It is thus understood that the container 10 according to the invention takes air into the internal space 20 between the flexible inner layer 26 and the inner surface 18 and that the dispensing cavity 56 makes it possible, when the first one-way valve 34 returns to its closed position, to limit the amount of product that remains outside the storage space 28.

[0110] Once dispensing is complete and the outer side wall 14 has returned to its initial, undeformed position, the user can pivot the lid 48 into its closed position, thereby increasing the sealing of the storage space in conjunction with the first one-way valve 34 in its closed state.

[0111] An advantage of such a configuration of the first one-way valve, combined with the shape of the dispensing cavity, is that it makes it possible to obtain a dispensing device without air return. The container is therefore an “airless” container, i.e. one with no air return after the product has been dispensed.

[0112] The use of the dispensing device without air return reduces contamination of the product contained in the storage space, thereby increasing its useful life, and also allows virtually all of the contained product to be recovered, even if it does not flow due to high viscosity. In addition, the use of the one-way valves as described allows the use of flexible containers, i.e. ones with a deformable outer side wall, allowing the user to retain the initial shape of the container.

[0113] Finally, the container as described, comprising the one-way valves and a flexible inner layer capable of being progressively detached from the wall, preferably by delamination, makes it possible to provide outer receptacles without shape limitations.

Claims

CLAIMS1. A container (10) for containing and dispensing a liquid or pasty product comprising: an outer receptacle (12) which comprises an outer side wall (14), an outer bottom (16) and an inner surface (18) which defines an internal space (20) of the outer receptacle (12), said outer receptacle (12) being elastically deformable as a result of pressure exerted on said outer side wall (14), and a sealed, flexible inner layer (26) extending inside the internal space (20) of the outer receptacle (12), the flexible inner layer (26) defining a storage space (28) for the product to be dispensed, and the flexible inner layer (26) being configured to retract as the product is dispensed, a product dispensing device (30) mounted on an upper end (24) of the outer receptacle (12), the dispensing device (30) comprising a support (32) and a first one-way valve (34), the support (32) defining an accommodating recess (52) for accommodating the first one-way valve (34), extended by a product outlet hole (44) for the product from the storage space (28), the container (10) being characterized in that the first one-way valve (34) comprises: an elastically deformable flexible membrane (70) held at its center by a fastening stud (72), said flexible membrane (70) comprising an upper face (82) and a lower face (84), a sealing seat (58) accommodated in a fastening cavity (54) of the accommodating recess (52) and sealingly fastened in the fastening cavity (54), the sealing seat (58) comprising a receiver (74) into which the fastening stud (72) is fitted, a free end (80) of said flexible membrane (70) cooperating with said sealing seat (58) of said first one-way valve (34) in a closed state of the first oneway valve (34) and so that said flexible membrane (70) can detach from said sealing seat (58) when the first one-way valve (34) is in a dispensing state,a dispensing cavity (56) of the accommodating recess (52) extending between the fastening cavity (54) and the outlet hole (44), the dispensing cavity (56) being defined by a main wall (36) of the support (32) and comprises indentations (86) suitable for allowing the passage of the product in the dispensing state of the first one-way valve (34), the dispensing cavity (56) comprising a hemisphere shape defined by the main wall (36) of the support (32).

2. The container (10) as claimed in the preceding claim, wherein the fastening cavity (54) of the accommodating recess (52) is defined by a cylindrical wall (60) of the support (32) which extends from the main wall (36) of the support (32) and into the internal space (20) of the outer receptacle (12).

3. The container (10) as claimed in either one of the preceding claims, wherein the indentations (86) are separated from one another by contact surfaces (88) formed on the main wall (36) in the dispensing cavity (56) so that the free end (80) of the flexible membrane (70) slides against the contact surfaces (88) when it is detached from the sealing seat (58).

4. The container (10) as claimed in any one of the preceding claims, wherein the indentations (86) extend substantially from a base of the hemisphere-shaped dispensing cavity (56) to substantially a top of the dispensing cavity (56).

5. The container (10) as claimed in any one of the preceding claims, wherein the flexible inner layer (26) is configured to delaminate from the inner surface (18) of the outer receptacle (12).

6. The container (10) as claimed in any one of the preceding claims, comprising a second one-way valve (96) installed in a foot (90) of the container (10) mounted on a lower end (22) of the outer receptacle (12) and at least covering the outer bottom (16), the foot (90) defining, with the outer bottom (16), an interspace (92) in fluid communication with the internal space (20) via at least one natural opening (94) formed in the outer bottom (16), the second one-way valve (96) being configured to allow the passage of a fluid only to the interspace (92).

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