CORK AND ITS METHOD OF MANUFACTURE

DESCRIPTION

Technical field

The present invention relates to a bottle stopper of the kind known as a cork and to its method of manufacturing.

More particularly the invention relates to a bottle stopper entirely made of natural cork and to the method of manufacturing it.

Prior art

As known, a cork is a kind of bottle stopper mainly intended to close glass bottles containing wine.

Especially in oenology, natural cork stoppers represent the most valuable and expensive kind of closure means, destined therefore to high-quality wines that generally are intended for a prolonged conservation or for ageing.

Actually, the method of manufacturing single-piece stoppers entirely made of natural cork is long and comprises several steps: according to the method, cork barked from the tree (which operation takes place manually, generally after about a ten year growth of the bark), is stacked in the form of boards (referred to as "plaques" in the field) and seasoned for a period from some months to up to two years, depending on the cases. At the end of the seasoning, cork is boiled to allow expansion of the structure and elimination of parasites contained in the bark. After a rest period, cork is then cut into strips, with a thickness substantially equal to the stopper height, in the direction of the width of the boards.

Subsequently, the stoppers are punched out from the strips by means of a cylindrical blade, the diameter of which substantially determines the stopper diameter.

Such operation is performed by cutting cork in a direction parallel to the growth rings of the tree, in a plane substantially parallel to the trunk to which the bark adhered.

Unused cork and the wastes from the cutting and the other working steps are collected for being used in the production of by-products, such as insulating and construction materials for the building industry.

The boards that, because of their insufficient thickness, cannot be used for producing natural cork stoppers, are partly used for making cork discs intended to form the bases (cork tops) of stoppers having a central body of different material.

For instance, EP 1 772 240 discloses a method of making cork discs about 6 mm thick for manufacturing cork tops. l According to the prior art, the discs are punched out from the boards in a direction perpendicular to the growth rings of the tree and consequently perpendicular to the cutting direction according to which the stoppers would have been punched out.

Once the nominal size of the product has been reached, a controlled thermal treatment is performed in order to sanitise the stopper itself. Such a treatment is indispensable in order to eliminate from the stopper surface soluble substances always present in cork, and especially moulds, bacteria and spores, if any, which would compromise the organoleptic properties of the stopper.

Actually, bottlers demand stoppers that are as far as possible neutral from the organoleptic standpoint, i.e., that are unable to cause the occurrence of unwanted reactions altering the taste of wine when contacting it when the bottle is closed.

In the case of natural cork stoppers, the primary responsible for such unwanted reactions is a parasite of cork oak, the Armillaria mellea. Growth of such fungus in the stopper causes the so-called cork scent in wine, which can be described as a smell similar to that of a mouldy newspaper, a wet dog or a damp cellar and is due to 2,4,6- trichloroanisole (TCA). Admitted trichloroanisole (TCA) amounts in cork stoppers typically do not exceed 4 ng/litre.

In order to avoid the above drawback, but also for cost saving, in the past stoppers have been developed by using particular treatments and materials other than cork.

Besides natural cork stoppers, also corks completely made of agglomerate, i.e. natural cork grains dispersed in an adhesive, corks made of agglomerate with one or two natural cork discs at their ends, referred to also as "two-disc corks", corks made of synthetic cork and corks made of plastic are at present widely used.

Corks made of plastic, while being free from the above problem, have the drawback that they allow wine oxidisation, due to an imperfect seal.

Also screw caps have become widespread, which ensure an almost perfect seal but, just because of such a characteristic, do not allow the passage of that minimum amount of air necessary in order to avoid the so-called "reduction smell" in wine, caused by the complete lack of aeration.

Agglomerate cork stoppers are made by using ground wastes of natural cork, bonded by means of adhesives. Production of agglomerate cork stoppers originates from two specific needs: on the one hand, to satisfy a growing demand of high-quality stoppers for oenological use by the market; on the other hand, to exploit the huge amount of cork that is discarded during the different steps of the cycle of production of natural cork stoppers (wastes exceed in the average 80% of the input material).

EP 0 481 155 for instance discloses a method of obtaining corks having a central body made of agglomerate and two discs of natural cork located at the ends.

This cork however has the drawback of demanding a high amount of adhesive, which increases the cost and prejudices the appearance and the sealing capacity.

Another example of a cork comprising a portion made of natural cork intended to remain in contact with wine and a portion made of agglomerate is disclosed in FR 1 186 245. This cork however has the drawback of causing the contact between wine and the adhesive layer.

Especially in case of champagne-like wines, the cork must not have cracks or porosity through which the wine or the gas can escape. In order to solve that problem, FR 543519 proposes a method of obtaining cork stoppers comprising a step of superimposing discs with different thicknesses, oriented so that adjacent discs have perpendicularly- oriented porosity.

Substantially to the same aim, FR 1 024 259 teaches fabricating cork stoppers by a method comprising the step of making a parallelepiped body having a cylindrical extension on which there are arranged bored discs oriented with their veins in the suitable direction, the discs being bonded by means of an adhesive so as to impart a suitable strength and a lack of porosity to the stopper.

WO 98/34679 discloses a method of making cork stoppers comprising the step of superimposing a number of natural cork sheets, the overall thickness of which corresponds to the height of the stopper to be obtained, and punching out the stoppers perpendicularly to the plane of the sheets.

FR 594 654 discloses a stopper comprising a cork disc arranged so that its pores are vertically oriented. A second disc, whose channels are arranged so that they are not aligned with those of the first disc, is glued onto the first disc to avoid seal losses. The stopper is completed with a central cork body having a wooden core and with a third disc glued onto the central body.

EP 1 393 869 discloses a multilayered natural cork stopper comprising three superimposed cork discs glued with perpendicularly-oriented cork veins.

FR 1 017 600 discloses an exemplary cork obtained by superimposing three discs and teaches making a stopper with a very high number of thin discs, since this structure apparently has exhibited greater advantages in the practical applications. The discs can be of made of natural or agglomerate cork and insulating discs of gutta-percha, paper etc. can possibly be interposed between the cork discs.

A method of producing cork stoppers is disclosed in EP 0 983 830. According to the teaching of this document, blocks obtained from the cork boards are boiled and then cut in order to obtain the stoppers. Always according to the teaching of this document, it is also envisaged to bond together the blocks in order to obtain rods from which the stoppers are obtained by cutting the rods to the desired length.

None of the above documents is however confronted with the problem of how to provide a cork that is made of superimposed discs of natural cork and is substantially free from the problem resulting from the production of 2,4,6-trichloroanisole (TCA).

Thus, it is the main object of the present invention to provide a cork made of superimposed discs, which solves the above problem.

Recent studies have moreover shown the commercial advantage determined by the use of closure means of natural cork, which advantage is originated by a substantially evocative effect on the consumer. Actually, a same wine, contained in bottles with different kinds of closure means, has been more appreciated by a sample of tasters when the closure was made of natural cork.

As stated above, natural cork stoppers have however the drawback of being expensive, of being subjected to the formation of trichloroanisole and, due to the direction of the cuts, of letting wine axially rise along the stopper when the bottle is laid horizontal or inclined for ageing.

Thus, it is a further, but not the last object of the invention, to provide a cork that does not have the drawbacks mentioned above and that is cheap and easy to be made, so that it can be industrially produced on a large scale.

Description of the invention

An advantage of the invention results from the choice of a specific thickness for the superimposed discs, typically a thickness of 6 to 8 mm, which makes the discs particularly capable of being sanitised without affecting their consistency and resiliency, this being a decisive factor for a good hermetic seal. According to the invention, thanks to the choice of a thickness in the above range, the results of the sanitation are comparable with those obtained when sanitising cork grains used for making agglomerate corks.

Thus, the choice of the thickness of the discs forming the cork, which is to be in the range of about 6 to 8 mm, is of essential importance for the attainment of the results to be reached by the invention.

Document FR 1 017 600 mentioned above on the contrary states that clear practical advantages are obtamed by using a high number of thin discs. Based on this teaching, the skilled in the art would have therefore been discouraged from using only six or seven discs with a thickness in the range 6 to 8 mm in order to manufacture a cork.

A thickness in the above range actually allows maintaining a sufficient consistency of the material during sanitation and the subsequent working steps. Lower thicknesses would result indeed in disc breakage or deterioration during the sanitation treatment because of the high temperature.

Document EP 0 983 830 mentioned above discloses a method of producing corks by cutting rods obtained by bonding cork blocks having the same thickness as the boards, after the blocks have been boiled. Based on this teaching, the skilled in the art would have not been induced to sanitise discs with a thickness in the range 6 to 8 mm in order to obtain a substantial organoleptic neutrality without compromising the mechanical properties.

This feature concerning the disc thickness thus solves the problem of how to provide a cork entirely made of natural cork discs, which is substantially neutral from the organoleptic standpoint.

A further advantage of the invention is the high sealing capability of the cork, resulting from the superimposition of discs of reduced thickness, but not too thin, which originate corresponding circumferential sealing zones.

Moreover, bottles closed with the cork according to the invention can advantageously be laid inclined or horizontal immediately after bottling, without need to wait for the period of 12 - 24 hours generally recommended by manufacturers of natural cork stoppers in order to allow the complete elastic return of cork and determine the proper seal. This results in a considerable time advantage and cost saving.

A further advantage of the invention results from arranging the discs in the cork according to their quality. Actually, by positioning high-quality discs at the cork ends and discs of progressively lower quality towards the centre, a product is obtained that has at the same time a high overall quality, since the end discs are in contact with the wine, and reduced production costs, since also low-quality cork can be used.

Advantageously, the cork according to the invention has substantially all advantages of a natural cork stopper at a considerably reduced cost.

If compared to a natural cork stopper, the cork according to the invention further has the considerable advantage of being substantially neutral from the organoleptic standpoint, since all cork discs are subjected to a sanitation treatment that, thanks to the reduced disc thickness, deeply penetrates into the material.

In a natural cork stopper, moreover, the wine tends to rise in the bark growth region, whereas the areas of fat accumulated during winter, which are transversally arranged in the cork according to the invention, form a barrier preventing wine rise.

Advantageously, in the cork according to the invention, wine is prevented from rising by the layers of fat, so that the internal layers of lower quality than the end discs substantially are not concerned by the wine rise.

This advantage is obtained since the discs are cut from the cork board according to a plane perpendicular to that used for cutting single-piece stoppers of natural cork, this allowing keeping the natural water-repellent fat layer unaffected. As known, for preventing the drawback of the axial wine rise along the cork, single-piece stoppers of natural cork are treated with water-repellent substances. Advantageously, thanks to the cork according to the invention, that treatment can be dispensed with.

Moreover, the cork according to the invention does not have the drawbacks of the agglomerate corks caused by the presence of a high amount of adhesive, which, as known, is a critical substance from the foodstuff standpoint.

Moreover, since cork being used is cut according to a plane perpendicular to that along which cork is cut for producing natural cork stoppers, the cork according to the invention advantageously has a high resiliency, surprisingly exceeding that of cork used for producing stoppers wholly made of natural cork and hence much higher than that of agglomerate corks, the resiliency of which is reduced due to the high amount of adhesive.

The cork made in accordance with the invention is moreover highly pressure- resistant, and thus it can be advantageously be used also for sparkling wines, in particular champagne-like wines.

Moreover, the cork according to the invention has a sealing capability higher than that attainable with an agglomerate cork stopper, even of the kind provided with cork discs at the ends.

A further advantage of the invention over the agglomerate cork stoppers is the reduced weight, mainly due to the lower amount of adhesive being used.

A further, but not the last, advantage of the cork according to the invention is given by the aesthetical appearance, which is highly homogeneous and cannot practically be distinguished from that of a natural cork stopper, notwithstanding the use of less expensive products.

Cork in thin sheets has today a limited market, since corks wholly made of agglomerate are preferred. An advantage of the invention is to provide a method allowing industrial utilisation of said wastes.

The cork made in this manner is moreover a substantially natural product, which can be recycled for instance in building industry as thermo-acoustical insulating material. Brief Description of the Figures

A preferred embodiment of the invention will be described by way of non limiting example with reference to the accompanying drawings, in which:

- Fig. 1 is a perspective view of a portion of a cork strip;

- Fig. 2 is a perspective view of a cork according to the invention;

- Fig. 3 is a side view of the cork shown in Fig. 2;

- Fig. 4 is a perspective view of a disc incorporated into the cork shown in Fig. 2

- Fig. 5 is a schematic diagram of the main steps of the method of manufacturing the cork according to the invention;

- Fig. 6 is a block diagram of a machine for manufacturing the cork according to the invention.

Description of a Preferred Embodiment

Referring to Fig. 1, a cork strip, generally denoted by reference numeral 11, comprises, starting from the inside, i.e. from the side that, before barking, was turned towards the tree trunk, and proceeding radially outwards, i.e. towards the outermost bark layer 13, a succession of alternating layers 15a, 15b.

Said layers 15a, 15b are defined by the so called "growth rings" and, in the case of cork oak bark, they comprise thicker summer growth layers 15a mainly consisting of porous material, and thinner winter growth layers 15b mainly consisting of substantially water-repellent material.

In case of cork boards with a thickness suitable for the production of corks, said layers 15a, 15b typically are in a number ranging from nine to twelve pairs, i.e., as many as are in the average the years of tree growth between two subsequent barking operations.

According to the invention, strip 11 is punched out in transverse direction, i.e. in the direction shown by arrows Fl, in order to obtain solid cork discs 17, in which layers 15a, 15b are parallel to each other and to the disc bases, and thus are substantially perpendicular to the disc axis.

Fig. 4 is a perspective view of a disc 17 obtained through the described operation.

As it can be appreciated, layers 15a, 15b are arranged parallel to each other and perpendicular to disc axis "T". 4237

Advantageously, thanks to such an arrangement, the so-called "winter" layers 15b form a barrier against the axial rise of liquid, in particular wine, through the cork.

With reference to Figs. 2 and 3, there is shown a cork 19 having a cylindrical body with circular cross section and made by superimposing, according to the invention, six or seven discs 17. The discs have a thickness "s" of about 6 to 8 mm, resulting in an overall cork height of about 42 to 48 mm, and a diameter "d" suitable for the neck of the bottles with which the cork is to be employed, for instance 24 mm,

Tests carried out have shown that discs with thickness below 6 mm are deformed and broken when subjected to the sanitation treatment, whereas thicknesses above 8 mm do not allow the sanitation treatment to deeply penetrate into the material, so that a proper disinfection would not be ensured.

The tests carried out have on the contrary shown that, by choosing thicknesses in the range of about 6 to 8 mm, is it is possible to completely sanitise the material by the sanitation methods at present employed in cork industry. According to the invention, each disc forming the cork structure is subjected to the sanitation treatment, with a considerable advantage over the conventional corks made by a single piece of natural cork.

The six or seven discs 17 are kept bonded together by an adhesive layer 21 which is interposed between adjacent discs 17 in liquid condition and is then cured.

According to the invention, cork 19 has good sealing properties since each disc 17 has a slightly convex external surface 23, which therefore gives rise to a good seal when the cork is in the bottle neck and is subjected to a radial compression.

Moreover, according to a preferred embodiment of the invention, discs 17 are advantageously distributed in the pack of six or seven discs in an order depending on their quality. More precisely, higher quality discs 17 are located at the cork ends, and lower quality discs 17 are located in the central portion.

Thanks to such a feature, it is advantageously possible to obtain high-performance corks at a considerably reduced cost.

According to a preferred embodiment of the method of invention, cork 19 is obtained by gluing together six or seven discs 17 of natural cork, previously subjected to a deep sanitation step, preferably according to a treatment by means of dry vapour, i.e. vapour in the absence of liquid, at a temperature exceeding 100°C.

Alternative sanitation methods, which however have the drawback of bleaching the corks, may include the use of peroxides (hydrogen peroxide and peracetic acid, sodium peroxide, etc.). The operation takes place in suitable "dry" operating equipment, by using a vapour formed of water, hydrogen peroxide and a catalyst in percentages depending on the production choices.

In the bonding step, discs 17 are superimposed onto each other after a certain amount of adhesive has been deposited on the concerned face of at least one of the discs, until obtaining a pack with six or seven superimposed discs.

In accordance with another embodiment of the invention, if several groups of discs 17 of different qualities are available, the bonding step is performed by superimposing discs 17 so that the discs located at the cork ends, i.e. the first and the last disc, are high- quality discs, and the remaining discs have a progressively decreasing quality as the cork central region is approached.

Referring to Fig. 5, according to this embodiment of the method of obtaining the corks according to the invention, a step is provided in which discs 17 are deeply sanitised in a sanitation station 101, preferably by means of a dry vapour treatment, i.e. by means of vapour in the absence of liquid, at a temperature higher than 100°C.

The discs are then transferred to a sorting station 103 in which they are preferably sorted for instance by means of an automatic device equipped with a video camera or another optical instrument, or manually.

According to the invention, sorting is performed according to the disc quality, preferably according to three categories CI, C2 and C3, corresponding to high, mean and low quality, respectively, which generally correspond to low, mean and high porosity, respectively.

In accordance with an alternative embodiment of the invention, this sorting step can be carried out before the disc sanitation step.

Through three transfer lines 107a, 107b, 107c, the sorted discs are transferred to a bonding station 109 equipped with an automated equipment.

One or more subsequent stations 111 are provided for carrying out the final method steps, including for instance a turning step in order to eliminate possible disc alignment errors and to obtain corks with a uniform side surface.

Turning now to Fig. 6, a machine for bonding discs 17 in accordance with the method described is shown.

Said machine is generally denoted by reference numeral 201 and it comprises at least one duct 203, 205, 207 for supplying cork discs 17, a bonding unit 209 having a distribution head 213 for distributing the liquid adhesive onto the upper disc face before the superimposition of the subsequent disc, and possibly a compression unit 211 equipped with a pusher 215 in order to axially compress the cork.

In the illustrated example, three supply ducts 203, 205, 207 have been shown for supplying the machine with discs 17a, 17b and 17c of quality CI, C2 and C3, respectively.

Machine 201 further includes a moving plane 217, which may for instance consist of a turntable or of a plane horizontally sliding in the direction shown by arrows F2.

It is clear that the above description has been given by way of non-limiting example and that further changes and modifications are possible without departing from the scope of the invention, as defined by the following claims.