EP1539603A1 - Closing stopper for containers - Google Patents

Abstract

Closing stopper for bottles of wine, formed by a cork body (2) and by a polyethylene sealing element having a mushroom shape with a shank (9) arranged inside a cavity (10) formed on a first face (4) of the body (2) and retained inside it by means of a plurality of axial and circumferential ribs (13). The disk-shaped head (1) of the sealing element (8) is arranged so as to cover the first face (4) and is slightly raised from the latter by a distance (S) so as to be elastically deformed when in contact with the internal surface of the neck (7) of the bottle (6) so as to exert a sealing action thereon.

Description

Closing stopper for containers DESCRIPTION The present invention relates to a closing stopper for containers, and in particular for bottles of wine. The stopper in question is intended to be used advantageously in industrial beverage bottling plants for closing the mouth of the containers, and in particular for sealing glass bottles intended for the storage and conservation of high-quality wine. The stopper according to the invention is suitable for use both in automatic corking machines and in apparatus of the manual type, also for private use.

At present as is known, the sealing of bottles is performed using stoppers of various kinds depending on the specific bottling requirements .

Traditionally, in the bottling industry the following are known for example: screw-on caps made of plastic or metal which require a thread formed externally on the neck of the bottle: metal crown caps which can be fitted onto the mouth of the bottles by means of crimping of their peripheral edge and which are provided with a seal which is known not to be entirely reliable over time and hence not suitable, for example, for the conservation of wine; synthetic stoppers which are made wholly or partly from plastic material which may be arranged on a cork body; and finally stoppers which are made entirely of cork and are considered particularly suitable for the conservation of quality wines.

Cork stoppers nowadays still remain the most suitable means for preserving wine, in particular when the wine is intended for long-term storage in a bottle.

The use of cork in the bottling industry, as is known, involves the need to subject the stoppers to a whole series of treatments aimed at preventing the occurrence of drawbacks which may adversely affect conservation of the wine or which may modify its taste and more generally its organoleptic qualities .

Some defects of cork stoppers may be attributable, as is known, to the fact that cork may release dust, fragments, paraffin or anomalous odours or generate mould or fungi which give the wine an unpleasant taste or smell which may be generally defined as "corky taste".

Anomalous odours may also be generated by the glues used to assemble the granules of cork which form the so- called agglomerate or composite stoppers (referred to in the technical jargon also by the name of "technical stoppers") or so-called bonded or laminated stoppers consisting of several cork parts which are joined together by means of an adhesive . In order to improve the quality of the stoppers and prevent unpleasant contamination of the wine, the cork is normally subjected to a whole series of measures which involve the entire production cycle thereof from stripping of the cork from the plants (and even prior to that, cultivation) to the subsequent processing steps such as seasoning, boiling and storage.

Obviously the individual production processes for the various types of stoppers must also pay particular attention to all those factors which may subsequently result in the release of undesirable substances into the wine.

The final quality of the stoppers may be greatly influenced by the contaminating substances which the cork may release, whether the corks be of the one-piece type and produced for example by hollow-punching machines or whether they be of the agglomerate type and produced by means of extrusion or moulding.

It is well-known that the contaminating substances are of microbiological origin, exogenous origin and technological origin.

In order to appreciate the complexity of the subject it is sufficient to consider that most of the microorganisms present in the cork are able to survive on dehydrated substrates and are able to develop owing to the constituents of the cork (polysaccharides, lipids, tannins, phenols) and the substances used in the treatment of the cork (paraffin, silicone, colouring agents, glues) .

"Substances of exogenous origin" are understood as being those substances which the cork is able to absorb from the environment in which it is stored, of the gaseous type such as phenol, naphthalene, etc., and which may then be released to the wine once the stopper is inserted inside the neck of the bottle. "Substances of technological origin" are those derived from the cork processing operations . For example disinfection and bleaching of the corks by means of chlorinated solutions may cause the formation of chlorophenols, and likewise it is known that treatments using sulphur dioxide may also be the source of numerous anomalies .

Particularly dangerous are the seasoning stages owing the development of microflora, but also the washing stages, in particular those using products such as potassium metabisulphite, calcium hypochlorite, oxalic acid, chlorine, hydrogen peroxide, sodium hydroxide, citric acid or high-temperature treatments for example by means of irradiation or microwaves .

Also, the surface treatments using paraffin and/or pure elastomer silicones in order to reduce the permeability to liquids and reduce the sugar/wine interchange may be a source of contamination of the wine.

A particularly unpleasant substance responsible for particularly severe contamination is for example 2,4,6- trichloroanisol which is one of the most frequent causes of the corky taste in wine and for this reason has been studied in detail .

The same treatments carried out on the corks may also adversely affect the elastic characteristics of the surface layers of the cork, subsequently reducing the sealing action thereof on the neck of the bottle .

In order to overcome these drawbacks associated with the use of cork stoppers - which moreover are considered indispensable in the quality and prestige wine industry - it is necessary to prevent any contact of the bottled wine with the stopper cork.

Some wine producers, especially for bottling wines which are not of a high quality and which must be consumed within a few years of bottling, have therefore begun to consider in an increasingly favourable manner, synthetic corks which in fact pose fewer problems and involve lower costs .

The choice of using a cork stopper instead of one which is even only partly synthetic is still influenced by partly emotional factors which are based on a widespread appreciation of completely "natural" products, i.e. represented by cork stoppers, in preference to synthetic or partly synthetic stoppers, represented by corks which are plastic or have a plastic component. As is known, at present on the market there are numerous types of synthetic stoppers . Obviously, completely plastic stoppers are the least appreciated by the consumer public who, as mentioned, are traditionally somewhat reluctant to associate a natural product, such as wine, with plastic parts, such as this type of stopper.

These stoppers generally have a poor sealing action on the neck of the bottle, which factor makes them unsuitable for the conservation of perishable substances and in particular the conservation of quality wine.

Plastic stoppers are known where the sealing action on the bottle is performed by means of annular flanges, although it is widely known that these do not have an elastic behaviour which is satisfactory and constant over time and therefore they are basically unreliable.

A further drawback of stoppers of this latter type is that they do not allow extraction from the neck of the bottle in a traditional manner by means of a corkscrew, but instead require a manual pulling action on a top part of the stopper which projects outside the bottle. Moreover, stoppers with a mixed structure are known, being especially designed to overcome the drawbacks of cork stoppers and plastic stoppers, said stoppers in a first embodiment being provided with a cork core and a lining of plastic material and in a second embodiment being composed of a cylindrical body made of cork and having fixed at one end a covering of plastic material which isolates, in a similar manner to the abovementioned lining, the wine from the cork, protecting it from possible contamination by the latter.

Aesthetically speaking, stoppers with a mixed structure of the type mentioned above appear to be much more similar to the cork stoppers than the completely synthetic corks and for this reason they may, over and above the technical aspects, be favourably regarded by the public.

In greater detail, stoppers with a plastic lining are manufactured by applying continuously a more or less thick homogeneous film, generally consisting of thermoplastic material over the entire surface of the stopper. This application, however, has not lead to satisfactory results both owing to the frequent tears which occur in the film during the sealing process and owing to the high costs of the process for manufacturing stoppers which are made in this way. In general, with reference to mixed-structure stoppers provided with a part or insert of synthetic material combined with a cork part, it may be stated that at the moment solutions able to ensure an optimum mechanical behaviour, in particular in relation to the elasticity required to provide a correct sealing action on the neck of the bottle and easy extraction of the stopper, using a normal corkscrew, are not known on the market . In fact often the known mixed-structure solutions are unable to ensure satisfactory joining of the plastic part to the cork part so much so that often the plastic insert remains inside the bottle during the stopper extraction operations . Embodiments of mixed-structure stoppers are known for example from the patents IT MI97A000346 and IT

1247147 which illustrate particularly complex solutions for ensuring fixing of the plastic part to the cork part.

In greater detail, the first solution envisages joining together of one end of the cork part with a plastic part advantageously provided with fixing fins engaging in a sealed manner in the cork part .

The second solution, however, envisages several embodiments of stoppers in which the volumes of the cork part and plastic part are substantially equivalent. In particular, a solution is envisaged with the cork part forming the core of the stopper and the plastic part provided all around it with the exception of the upper surface, as well as a solution with an upper part consisting of cork and shaped in the manner of a mushroom and a bottom plastic part combined with the first part and shaped in a matching manner with respect thereto.

Italian patent IT 1287216 illustrates a stopper in which the cork part is provided with annular grooves able to receive corresponding projections provided on an external sleeve of synthetic material . The latter is closed at the bottom end of the stopper intended to be inserted into the neck of the bottle, while it is open at the top so as to allow extraction of the stopper, by acting on the cork part .

The stopper solutions described hitherto in practice pose difficulties with regard to extraction and do not have an optimum sealing action with regard to the passage of air or gas . Many mixed-structure solutions which are commercially available are obtained with the synthetic material part composed of materials which are of limited elasticity and particularly rigid and which, once they have undergone compression during sealing, do not subsequently allow easy extraction of the stoppers themselves in particular at low temperatures when, as is known, thermoplastic synthetic materials become particularly hard and are no longer able to be deformed and pass through the neck of the bottle. In order to overcome this problem the synthetic materials from which some solutions of mixed-structure stoppers are made are less rigid, but on the other hand are not made of material which is entirely compatible, from an alimentary point of view, with the liquids contained in the bottles since they release more easily undesirable substances than more rigid materials .

French patents FR 2644142, FR 1100335, FR 1534142 and FR 1068263 describe various solutions of stoppers provided with a cylindrical body made of cork covered at one or both ends with a disk of plastic material. The latter is advantageously of the elastomer type and preferably consists of silicone in the patent FR 2644142 and polyethylene in the patent FR 1100335.

A similar solution is also described in the French patent FR 983488 which, however, also envisages a circular cavity formed on the bottom of the cork body to which a capsule of impermeable and unalterable synthetic material can be fixed.

The international patent WO 01/14219 also describes a cork stopper solution where it is envisaged using a disk of synthetic material. However, in this case, the disk is fixed at the top to the cork part, in particular with a layer of glue for alimentary products, so as to be situated outside the bottle once the stopper has been inserted inside the neck. However, the drawbacks associated with the release into the wine, by the cork, of undesirable substances still remain unresolved.

A solution entirely similar to these latter solutions is also that described in international patent WO 00/34140. The latter envisages the insertion of an elastomer material, substantially incompressible, into a circular cavity formed at one end of the cork body, having a diameter slightly less than that of the surface of the stopper. In so doing, as a result of compression of the stopper following closing, elastic deformation of the elastomer material occurs, resulting in the latter forming a seal on the internal surface of the bottle.

The patents WO 00/26103 and US 6,127,437 describe stoppers made entirely from synthetic materials with optimum mechanical sealing properties.

In particular, the solution described in the patent . WO 00/26103 envisages that the stopper is composed of two parts both consisting of synthetic material and rigidly joined together, preferably the innermost one of said parts being made of more rigid plastic. From an aesthetic point of view, these stoppers made entirely of plastic, as already explained above, are not held in particular high esteem by the consumer public, especially if they are intended to seal bottles of wine of a certain quality.

In this situation, the object underlying the present invention is therefore that of eliminating the drawbacks of the known art mentioned above, by providing a closing stopper for containers which allows the organoleptic properties of the beverages contained in the containers to be protected from possible contamination by a cork part of the stopper itself.

Another object of the present invention is that of providing a stopper able to provide an optimum mechanical seal preventing the passage of air and/or gas affecting the container .

Another object of the present invention is that of providing a stopper which has optimum mechanical properties allowing easy insertion and easy extraction thereof into/from the neck of a bottle, in particular by means of a normal corkscrew.

Another object of the present invention is that of- providing a stopper which is simple and inexpensive to produce . Another object of the present invention is that of providing a stopper which preserves the typical and advantageous characteristics of cork, but at the same time overcomes the drawbacks thereof associated with the emission of undesirable substances . Another object of the present invention is that of providing a stopper which is visually pleasing.

These objects, together with others which will emerge more clearly below, are achieved by a closing stopper for containers, in particular for bottles of wine, which comprises: a cork body with an elongated shape having a lateral surface and a first and a second end face intended to be oriented respectively towards the inside and the outside of a container; a sealing element made of polymer material with a substantially mushroom- shaped form, having a shank arranged inside a cavity formed on the first end face, the shank comprising a plurality of ribs intended to keep the shank itself fixed . to the cork body inside the cavity; and at least one disk-shaped head which is fixed to the shank, arranged so as to cover the first face, separate therefrom, and capable of being elastically deformed when in contact with the container so as to exert a sealing action thereon .

The technical features of the invention, in accordance with the abovementioned objects, may be clearly understood from the contents of the claims indicated below and the advantages therefore will emerge more clearly from the detailed description which follows,. with reference to the accompanying drawings, showing some purely exemplary and non-limiting embodiments thereof in which:

PIG. 1 shows a sectioned side view of a first embodiment of the closing stopper for containers according to the present invention; FIG. 2 shows an exploded view of the stopper according to Fig. 1;

FIGS. 3a, 3b, 4a, 4b, 5a, 5b, 6a and 6b show, respectively, a prospective view and a side view of four examples of embodiment of a detail of the stopper according to Fig. 1, relating to a first type of mushroom-shaped insert;

FIGS. 7a, 7b show respectively a perspective view and a side view of a detail of the stopper according to

Fig. 1, relating to a second type of mushroom-shaped insert;

FIGS. 8a, 8b, 9a, 9b show respectively a perspective view and a side view of two examples of embodiment of a detail of the stopper according to Fig. 1, relating to a third type of mushroom-shaped insert; FIG. 10 shows an overall side view of the stopper according to Fig. 1 inserted in the neck of a bottle.

With reference to the drawings, 1 denotes in its entirety a closing stopper for containers according to the present invention. The stopper 1 is particularly suitable and advantageously used for sealing bottles of wine, although obviously it may be likewise intended for sealing any type of container and for conserving any type of alimentary and non-alimentary liquid, without thereby departing from the scope of protection of the present patent .

In accordance with the figures of the accompanying drawing, the stopper 1 is provided with a cork body 2, as the main element, having an elongated substantially cylindrical shape with a side surface 3 and two end faces, a first one 4 and second one 5 of which are respectively intended to be oriented towards the inside and towards the outside of a bottle 6 once the stopper 1 has been introduced inside its neck 7. According to the present invention, the stopper 1 is composed moreover of a sealing element 8 made of polymer material with a substantially mushroom-shaped form.

More particularly, the abovementioned sealing element 8 is provided with a shank 9 arranged inside a cavity formed on the first end face 4 and a disk-shaped head 11 fixed to one end 12 of the shank 9 and arranged so as to cover the first face 4.

The shank 9 is in turn provided with a plurality of ribs 13 able to keep the sealing element 8 fixed to the cork body 2 inside the cavity 10.

The head 11 is slightly raised at a distance S from the first end face 4 so as to be able to be deformed elastically (see Figure 10) when in contact with the internal surface of the neck 7 of the bottle 6 during sealing.

The elastic deformation of the head 11 allows the sealing element 8 to exert a pressure on the internal surface of the neck 7 of the bottle 6.

Operationally speaking, the cork body 2 exerts, as in the case of cork stoppers of the traditional type, a notable mechanical sealing action on the neck 7 of the bottle 6.

This action, as is well known, is due to the considerable frictional force which cork is able to exert on glass owing to its high degree of elasticity and also owing to its characteristic porous basic structure formed by a multiplicity of tiny suction cups.

The sealing element 8, on the other hand, is formed, as will be better illustrated below, by an impermeable material able to slide in contact with the internal surface of the neck 7 of the bottle 6 and therefore is not able to exert any significant mechanical retaining action on the neck 7 of the bottle 6.

Operationally speaking, once the stopper 1 is inserted in a traditional manner inside the neck 7 of the bottle 6, the head 11 is physically located so as to fully separate the cork body 2 from the liquid contained in the bottle 6.

In this way, the head 11 is able to isolate perfectly the cork body 2 from the liquid in the bottle 6, protecting the latter from possible emissions and/or undesirable contamination by the cork, for example dust and/or substances with undesirable aromas .

Moreover, advantageously, the arrangement of the head 1 so as to cover the face 4 of the cork body 2 limits considerably the permeability of the stopper 1 with respect to the passage of air or gas and in particular with regard to the passage of oxygen.

In accordance with a further characteristic embodiment of the present invention, the diameter D of the disk-shaped head 11 has dimensions larger than the internal diameter P of the neck 7 of the bottle 6 and dimensions smaller than the diameter d of the first face 4 of the cork body 2. In this way, on the face 4 there is defined an annular rim 13 which is free from the covering of the head 11 and which allows the stopper 1, during sealing, to perform varied compression of the cork body 2 with respect to the sealing element 8. This makes it possible to compress the cork body 2 more than the head 11 so as to provide an optimum mechanical seal on the internal surface of the neck 7 of the bottle 6.

Alternatively, the disk-shaped head 11 may have dimensions which are substantially equal to the first face 4 of the cork body 2 which therefore will be entirely covered by a layer of polymer material .

In any case, during compression of the stopper 1 relative sliding of the surface of the first cork face 4 and the opposite surface 11 made of polymer material takes place with consequent varied compression of the cork body 2 and the sealing element 8.

The aforementioned distance S may therefore also have very small values provided that it allows relative sliding of the abovementioned two surfaces. If necessary, the cork surface of the first face 4 and the polymer-material surface of the head 11 may also be in contact with each other, provided that they maintain the possibility of sliding one on top of the other. The different diameter of the head 11 with respect to the cork body 2 is justified by the different operating functions of the two elements as by the different materials from which they are formed.

The head 11 is in fact compressible to a limited extent and is elastically deformed as illustrated in Figure 7 only so as to allow perfect adhesion to the neck 7 of the bottle 6.

The cork body 2, however, must be capable of a high degree of elastic compression so as to allow, during sealing, firstly a significant reduction in the diameter and then a rapid elastic return able to determine an important gripping action on the internal surface of the neck 7 of the bottle 6.

As is known, many fizzy wines and in particular spumante have dissolved in them a certain quantity of gas and for this reason must be kept under pressure inside the bottles with stoppers able to prevent any seepage of gas. The possibility of varying the compression of the cork part 2 with respect to the part 8 made of synthetic material allows optimum seals to be achieved, subjecting the cork to high compressive forces without affecting the integral nature of the part 11 made of synthetic material which, as mentioned, does not require a correspondingly high compression in order to isolate the wine from the cork body 2. The sealing element 8 is made of a material which is perfectly compatible with alimentary substances and, in particular, in accordance with a preferred embodiment of the present invention, it consists of low density polyethylene, the thermal and mechanical properties of which are summarised in the table shown below:

Alternatively, the sealing element 8 may for example be made of high-density polyethylene or polytetrafluoroethylene .

In accordance with the first embodiment of the stopper illustrated by way of example in the accompanying Figures 3 to 6, the configuration of the ribs 13 is advantageously composed of first ribs 13a which extend axially along the extension of the shank 9. They are four in number and are arranged at 90° with respect to each other and are able to prevent rotation of the sealing element 8 about the axis Y of the shank 9.

Fixing ribs or teeth 13b are also provided on each rib 13a for preventing the shank 9 from coming out of the cavity 10.

Advantageously, in order to allow easier insertion of the shank 9 in the cavity 10 and provide the sealing element 8 with a suitable mechanical strength, it is envisaged that the free end 14 of the shank 9 is tapered in the form of a cone and that the other end 12 arranged in the vicinity of the head 11 is reinforced by means of a base 15 having preferably a shape in the form of a step or a substantially frustoconical chamfer.

Figures 7a and 7b show a second embodiment of the stopper 1 according to the invention, which is composed of several column elements 16 which are separate from each other, arranged close together and rigidly connected to the head 11 at their base 15. The column elements 16 are in turn provided with second fixing ribs or teeth 13b for preventing the shank 9 from coming out of the cavity 10. Moreover, Figures 8 and 9 show a third embodiment of the stopper according to the invention, in which the shank 9 has a substantially tubular shape and correspondingly the cavity 10 (not shown) has a matching annular shape. In accordance with this example, the first and the second ribs 13a and 13b extend correspondingly vertically in the direction of the axis Y of the shank 9 and circumferentially around the shank 9 itself.

In accordance with a further constructional feature of the present invention, shown by way of example in Figure 1 alone, the surface 17 of the disk-shaped head 11 opposite the cork body 2 has formed in it a circular groove 18 able to facilitate the elastic deformation of an annular edge 19 of the said head 11. Advantageously, the abovementioned annular edge 19 has a peripheral portion 20 which is externally tapered in particular with a profile having a concavity or a step 21 directed towards the outside of the stopper 1.

This solution advantageously allows improved adhesion of the head 11 on the neck 7 of the bottle 6 with deformation of the sealing element 8 which affects mostly the zone of the annular edge 19.

Operationally, during introduction of the stopper inside the neck of the bottle, for example by means of an automatic corking machine, there is a notable compression of the cork body 2 and a lesser compression of the sealing element 8 with elastic deformation of the head 11 as shown in Figure 10, which slides in contact with the internal surface of the neck 7 of the bottle 6 until it stops forming a seal thereon.

Once it has been pushed and released inside the bottle 6, the cork body expands completely, keeping the stopper 1 fixed inside the neck 7, while the head 11 provides an optimum hydraulic seal on the glass, preventing the passage of air as well as preventing contamination of the wine by means of the undesirable substances which may be emitted by the cork.

The subsequent operation of extraction of the stopper 1, performed with a corkscrew of the conventional type, in accordance with the invention, does not encounter any obstacle due to the presence of the sealing element 8.

Numerous tests have shown in fact that the form of the shank 9 described above and distinguished by a plurality of ribs 13a and 13b allows the corkscrew to rotate about the shank 9 without ever managing to expel it from the cavity 10 into which it is introduced.

Advantageously the height h of the shank 9 is between a half and a quarter of the overall height H of the stopper 1. This choice arises from the need to ensure that the properties of the cork body 2 remain as intact as possible in order to allow it to retain the necessary elastic characteristics indispensable for exerting a significant compressive and frictional force on the neck 7 of the bottle 6.

The invention therefore achieves the predefined objects.

Obviously it may also assume, during its practical realization, forms, dimensions and configurations different from those illustrated above also depending on the type of bottle (Bordeaux, spumante, etc.) without thereby departing from the scope of protection of the present patent . Moreover all the details may be replaced by technically equivalent elements and the dimensions, forms and materials used may be any according to requirements.

Claims

1. Closing stopper for containers, in particular bottles or the like, which comprises:

- a cork body (2) with an elongated shape having a lateral surface (3) and a first and a second end face (4,

5) intended to be oriented respectively towards the inside and the outside of a container (6) ;

- a sealing element (8) made of polymer material with a substantially mushroom-shaped form, having: - a shank (9) arranged inside a cavity (10) formed on said first end face (4) , said shank (9) comprising a plurality of ribs (13) intended to keep said shank (9) fixed to said cork body (2) inside said cavity (10) ; - and at least one disk-shaped head (11) which is fixed to said shank (9) , arranged so as to cover said first face (4) , separate therefrom, and capable of being elastically deformed when in contact with said container (6) so as to exert a sealing action thereon.

2. Stopper according to Claim 1 , in which the diameter (D) of said disk-shaped head (11) is smaller than the diameter (d) of said first face (4) so as to define an annular rim (13) not covered by said sealing element (8) .

3. Stopper according to Claim 1 or 2 , in which the diameter (D) of said disk-shaped head (11) has dimensions greater than the diameter (P) of the neck (7) of said container (6) so as to allow said sealing element (8) to be deformed during sealing of the container (8) , adhering to its internal surface.

4. Stopper according to any one of the preceding claims, in which said sealing element (8) is made of any one of the following materials: low-density polyethylene; high-density polyethylene; polytetrafluoroethylene .

5. Stopper according to any one of the preceding claims, in which said disk-shaped head (8) is provided with a circular groove (18) formed in the surface (17) opposite the cork body (2) and able to facilitate elastic deformation of its annular edge (19) .

6. Stopper according to Claim 5 , in which said annular edge (19) has an externally tapered peripheral portion (20) .

7. Stopper according to Claim 6 , in which said peripheral portion has a profile with a concavity or step

(21) directed towards the outside of the stopper (1) .

8. Stopper according to Claim 1, in which said ribs (13) comprise first ribs (13a) which extend substantially axially along the extension of said shank (9) , so as to prevent rotation of the latter about its axis .

9. Stopper according to Claim 1, in which said ribs (13) comprise second ribs (13b) which extend substantially perpendicularly with respect to the extension of said shank (9) , so as to prevent the latter from coming out of said cavity (10) .

10. Stopper according to Claim 8, in which said first ribs (13a) are provided with teeth (13b) for preventing said shank (9) from coming out of said cavity (10).

11. Stopper according to Claim 1, in which the free end (14) of said shank (9) is tapered in the form of a cone.

12. Stopper according to Claim 1, in which said shank (9) is provided in the vicinity of the end (12) fixed to said head (11) with a reinforcing base (15) .

13. Stopper according to Claim 1, in which said reinforcing base (15) has a chamfered form with a substantially frustoconical shape.

14. Stopper according to Claim 1, in which said shank (9) has a substantially tubular shape and correspondingly said cavity (10) has a matching annular shape .

15. Stopper according to Claim 1, in which said shank (9) is formed by several column elements (16) which are separate from each other, arranged close together and rigidly connected to said head (11) at one of their ends ( 12 ) .

16. Stopper according to Claim 15, in which said column elements (16) are provided with teeth (13b) for preventing said shank (9) from coming out of said cavity (10) .

17. Stopper according to Claim 1, in which the height (h) of said shank (9) is between a half and a quarter of the overall height (H) of said stopper (1) .

18. Stopper according to Claim 1, in which said sealing element (8) is made of low-density polyethylene having a composition distinguished by a hardness factor of between 32 and 42 Shore.

19. Stopper according to Claim 1, in which said disk-shaped head (11) is arranged raised from said first- face (4) by a distance (S) .