METHOD FOR MANUFACTURING STOPPERS

Technical field

The present invention relates to a method for manufacturing stoppers, particularly suitable for bottles. Background art

It is known that bottles of wine, liqueur, brandy or others are closed by applying to the neck of such bottles stoppers which, depending on production requirements, are made of cork, plastics or composite material or are of the crown type. The most widespread stoppers made of cork or plastics or a specific combination thereof are inserted almost entirely in the neck of the bottle, from which they are extracted by means of corkscrews of the type known in the jargon as screw, spiral or worm.

Crown-type stoppers are instead applied to the top rim of the neck of the bottle, with respect to which they remain always external in order to be removed by means of so-called bottle openers, which are suitable for opening the bottle quickly and effectively.

Stoppers placed inside the neck of the bottle comprise a generally cylindrical contoured body, which in many cases is made entirely of cork or plastic material.

However, there are types of stopper which are composite, so to speak, and comprise both parts made of cork and parts made of synthetic material.

Further, exclusively synthetic stoppers in turn can be classified into stoppers made of a single plastic material and stoppers made of several plastic materials.

Among these last, there is a particular category of stopper in which each stopper comprises a main part made of a first plastic material and a remaining part made of a second plastic material which is different from the first one. The main part is the contoured body introduced above and has

technical properties, such as mechanical strength, which are superior to those of the remaining part, which constitutes the outer layer of the stopper, a sort of polished and smooth enclosure which surrounds completely the contoured body. This embodiment has been studied both to provide extreme toughness to the region of the stopper that is subjected to compression during extraction from the neck of the bottle and to facilitate as much as possible the sliding of the stopper within the neck both during extraction and conversely during insertion. In any case, any synthetic stopper is formed by a mixture of petroleum-derived thermoplastic materials known as elastomers, which are aggregated by means of an injection-molding method.

Synthetic stoppers are preferable over cork stoppers, since they do not crumble, do not form dust, cannot be attacked by molds or bacteria, are absolutely immune to any kind of release and further offer an excellent and durable oxygen barrier, preserving over time the organoleptic characteristics of the liquid contained in the bottle.

In relation to cork stoppers, synthetic stoppers have the additional advantage of being customizable by coloring or by ink printing which applies for example trademarks or logos.

However, currently commercially available synthetic stoppers have some drawbacks, which are linked mostly to the method by means of which they are obtained.

A first drawback is that the thickness of the plastic enclosure that surrounds the contoured body of known stoppers is not uniform and constant, although specific variations of injection-molding methods have been devised which are known as sandwich methods; one of these variations is known from Italian patent ITl 316150.

These constructive variations allow to obtain a thickness of the outer layer which is more uniform than in previous stoppers but still not entirely

constant.

Another drawback of the background art that most closely approximates the invention, given in the cited Italian patent, arises from the fact that the outer layer with lower mechanical strength completely covers the contoured body and therefore also covers the front parts that must bear the compression and traction stress during extraction of the stopper from the bottle.

This entails the obtainment of stoppers of less than optimum quality, in addition to an increase in the constructive complexity of the stopper which appears to be unjustified and useless in terms of its intended use, with the consequent cost increase. Disclosure of the invention

The present invention seeks to obviate the limitations noted above.

The aim of the present invention is to provide a method for manufacturing stoppers made of composite plastic material which provides a finished product which has an outer layer which is still suitable to facilitate the sliding of the stoppers on the neck of the bottle but has a more constant and uniform thickness than that ensured by known methods.

Within this aim, an object of the present invention is to provide a stopper which, with respect to the equivalent background art, has an embodiment that is more suitable and adequate for the stresses that it must withstand during extraction from the neck of the bottle.

Another object of the invention is to provide a method for manufacturing stoppers which is simpler to perform than known methods. Another object of the invention is to provide a method which can be performed at lower costs than the background art, all other factors involved being equal.

This aim and these and other objects which will become better apparent hereinafter are achieved by a method for manufacturing stoppers according to claim 1, to which reference is made for the sake of brevity.

Other detail characteristics of the method according to the invention are provided in the corresponding dependent claims.

The stopper obtained with this method and whose essential characteristics are given in claim 15, to which reference is made again for the sake of brevity, is also an integral part of the present invention.

Advantageously, the method according to the invention provides stoppers made of composite synthetic material, suitable for bottles, which comprise an outer layer made of suitable plastic material which has a substantially constant thickness which is more regular and uniform than the one obtained in the background art.

Also advantageously, the invention provides a stopper made of plastic material which is more suitable than known types of stopper to bear the compression and traction stresses applied to it during extraction from the neck of the bottle by means of a corkscrew operated by the user. This is due to the fact that differently from known stoppers, the front surface to which these stresses are applied belongs to the contoured body made of plastic material with high mechanical strength instead of the outer layer made of a different synthetic material, which is inferior in this regard.

On the other hand, however, the outer layer of the stopper according to the invention is smooth and without porosity, thus facilitating the sliding of the stopper during insertion and extraction in and from the neck of the bottle.

Equally advantageously, the method according to the invention allows to obtain a quality final product with an addition of plastic material, which constitutes the outer layer of the stopper, which is smaller than in the background art, thus reducing production times and the associated costs.

Advantageously, moreover, the method according to the invention allows to obtain the outer layer of the stopper by providing the typical operations of the method for molding with two plastic components which is known in the field as sandwich method.

Brief description of the Drawings

Further characteristics and advantages of the method claimed herein will become better apparent from the following description of a preferred embodiment of the invention, given by way of non-limiting example in relation to the accompanying drawings, wherein:

Figure 1 is a longitudinal sectional view of a step of the method according to the invention;

Figure 2 is a longitudinal sectional view of another step of the method according to the invention; Figure 2a is a longitudinal sectional view of the stopper according to the invention, obtained at the end of the method according to the invention. Ways of carrying out the invention

The method for manufacturing a stopper, suitable in particular for bottles containing wine and shown in Figure 2a, where it is generally designated by the reference numeral 1, comprises the following operations:

- preparing a mold 8 which is suitable to produce the stopper 1 and forms internally a cavity 2 which is connected to the outside environment by means of a lateral hole 3;

- coupling to the mold 8 a plug 4, which is inserted in the cavity 2 for a predefined length L on the opposite side with respect to the lateral hole 3 and is allowed to slide within the cavity 2;

- coupling an injector, not shown for the sake of simplicity, to the mold 8 at the lateral hole 3.

According to the invention, the method further includes the following operations:

- forming a peripheral slot 6 of substantially constant thickness between the inner wall 2a that delimits the cavity 2 and the outer wall 4a of the plug 4;

- performing a first injection of plastic material within the peripheral slot 6 in order to obtain a perimetric border 7 which extends over the

predefined length L;

- freeing the cavity 2 from the plug 4 by an extent equal to the predefined length L, forming a volume which is delimited by the perimetric border 7, as shown in Figure 2; - performing a second injection of plastic material in the volume 9 delimited by the perimetric border 7 in order to obtain a contoured body 10 and ultimately the stopper 1 shown in Figure 2a once extraction from the mold 8 has occurred.

The cavity 2 divides the mold 8 into two mold parts 81, 82 and is closed at one end by the plug 4, which protrudes from the mold 8 by an extent which varies in length during the method.

The mold parts 81, 82 are mutually separated and are connected at one end by means of the plug 4 and at the opposite end by means of a lid 5.

According to other embodiments, not shown in the drawings of the present application, the mold parts can be formed monolithically with each other.

In the specific case, the predefined length L of the insertion of the plug 4 into the cavity 2 corresponds substantially to the entire length of the cavity 2, but it is evident that in other embodiments of the invention, not shown, said length may be shorter.

The peripheral slot 6 starts, preferably not exclusively, from the lateral hole 3 and has an annular shape, so that the contoured body 10 and therefore the stopper 1, at the end of the method according to the invention, have a circular shape. In practice, the peripheral slot 6 is formed by the fact that the plug 4, in the part inserted in the cavity 2, has a smaller diameter than the cavity 2 itself by an extent equal to the thickness that has been predefined for the outer layer 7 of the stopper 1.

The freeing of the cavity 2 from the plug 4 and the second injection occur simultaneously.

Substantially, therefore, freeing the cavity 2 from the plug 4 consists in allowing the plug 4 to slide from the inside of the cavity 2 toward the outside during the second injection by means of the plastic material injected into the volume 9. The plug 4 exits from the cavity 2 by a maximum length which is equal to the value of the predefined length L and until it reaches, in a short time, the stroke limit position 11.

The stroke limit position 11 is located within the cavity 2 and comprises a step 12, which protrudes from the inner wall 2a that delimits the cavity 2, and a tooth 13, which protrudes from the outer wall 4a of the plug 4 proximate to the end 4b thereof which faces the lateral hole 3.

The first and second injections consist of an injection molding.

In a preferable but non-limiting manner, the plastic material injected during the first injection is different from the plastic material injected during the second injection.

In greater detail, the plastic material of the second injection has a higher mechanical compression strength than the plastic material of the first injection.

In any case, the synthetic materials used in the method according to the invention are of a type which is known to the person skilled in the art, in particular mutually different mixtures of thermoplastic materials known as elastomers.

According to the preferred embodiment described here of the method according to the invention, the injector comprises two injection nozzles 14 and 15 which are formed in the lid 5; the first nozzle is connected to the peripheral slot 6 formed in the cavity 2 and the second nozzle is functionally connected to the plug 4 and faces it.

The first injection nozzle 14 is used during the first injection, at the end of which it is no longer affected by the flow of plastic material, while the second injection nozzle 15 is used in the second injection.

The method according to the invention further comprises an operation for reinserting the plug 4 into the cavity 2 by the predefined length L, which is performed after the second injection is completed and after the stopper 1 has been extracted from the mold 8. Reinsertion occurs automatically by way of actuation means, which are not shown for the sake of convenience in description and are associated with the end 4c of the plug 4.

Once the method according to the invention has ended, the stopper 1 shown in Figure 2a, which is the subject of the present invention, is thus obtained.

As can be seen, the stopper 1 comprises a contoured insert 10, which is made of a first plastic material and is suitable to be associated with a container, not shown, in order to close it; said insert has a lateral surface 10a and two front surfaces 10b, 10c which are mutually opposite and spaced by means of the lateral surface 10a.

According to the invention, the stopper 1 comprises an outer layer 7, which is made of a second plastic material which covers the lateral surface 10a of the contoured insert 10.

As already mentioned, the second plastic material is preferably but not necessarily different from the first plastic material.

It is specified that the coloring of the contoured insert 10 and of the outer layer 7 of the stopper 1 may be any and that the colorings may be mutually different or not.

From what has been described above it is therefore evident that the method for manufacturing stoppers and the corresponding stopper according to the invention achieve the previously mentioned aim and objects and provide the above mentioned advantages.

During production, it is possible to apply changes in application to the method according to the invention for manufacturing stoppers, said changes consisting for example of a different method of freeing the cavity

from the plug.

In addition to this, the number of cavities formed inside the mold and accordingly the number of plugs and injectors can be more than one, and this does not compromise the advantage provided by the present invention. Further, there can be applicative solutions of the method according to the invention in which the profile of the cavity, and accordingly the profile of the plug shaped complementarily thereto, are different from the shape described previously, which as mentioned is circular.

Finally, it is evident that many other variations can be made to the method according to the present invention without thereby abandoning the principles of novelty that are inherent in the appended claims, and likewise it is evident that in the practical embodiment of the invention the materials, shapes and dimensions of the described details may be any according to requirements and can be replaced with other technically equivalent ones. The disclosures in Italian Patent Application No. VI2006A000156, from which this application claims priority, are incorporated herein by reference.