EP2943418A1

EP2943418A1 - Cap with tamper evident seal for containers, container comprising said cap and preform for producing said container

Info

Publication number: EP2943418A1
Application number: EP13828873.3A
Authority: EP
Inventors: Vieri Ceccherini
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-01-08
Filing date: 2013-12-23
Publication date: 2015-11-18
Anticipated expiration: 2033-12-23
Also published as: WO2014108781A1; US20150344192A1; ITFI20130301A1; EP2943418B1; ITFI20130005A1

Abstract

There is described a container (1) with a thread (5) for a screw closing cap (3). The container has a neck (1A) with a lower shoulder (1X) that extends from the external surface (1Z) of the neck, on which the thread (5) is formed toward the inside.

Description

"CAP WITH TAMPER EVIDENT SEAL FOR CONTAINERS, CONTAINER COMPRISING SAID CAP AND PREFORM FOR PRODUCING SAID

CONTAINER"

DESCRIPTION

TECHNICAL FIELD

The present invention relates to plastic containers, in particular plastic bottles for natural mineral water, or plastic bottles for sparkling mineral water and also for other beverages.

State of the art

The use of plastic bottles for packaging mineral water or other beverages is very widespread. Plastic bottles are normally provided with a screw cap, or capsule, which is engaged to the bottle and which has a tamper evident seal or security band that is broken when the bottle is opened for the first time and provides the consumer with a guarantee of the integrity of the bottle content at the time of purchase.

Modern large bottling plants fill tens of thousands of bottles per day, and in some cases hundreds of thousands of bottles and consequently they consume a large number of this type of container. There is constant search for new ways of reducing the weight of each bottle and of each cap, firstly to reduce production costs and secondly to also reduce the environmental impact of this type of packaging, considered that not all plastic bottles are recycled.

Plastic bottles of this type normally have a threaded neck and, between the thread and the body of the bottle, two perimeter collars or annular ridges, the one used to couple the tamper evident seal and the other to handle the bottles in the filling plants.

EP-A-2207722 describes a plastic bottle wherein the neck of the bottle has only one perimeter collar or annular ridge used both to engage the bottle with handling and conveying members inside the filling plant, and to constrain the tamper evident seal. To allow handling of the bottle, between the threaded neck of the bottle and the annular ridge there is provided an annular groove or recess in which the mechanical handling members engage.

The use of a single perimeter collar or annular ridge, in place of the conventional conformation with double collar, enables the weight of each bottle to be reduced by a few grams and consequently the quantity of plastic used each year by the packaging plant to be reduced by many tons.

WOA-2009/146567 describes a cap with tamper evident seal for a bottle, said cap comprising a lateral wall and an internal thread formed on an internal surface of the lateral wall. The lateral wall of the cap comprises a security element in the form of a tab that cooperates with the thread of the bottle, so as to be irreversibly altered when the screw cap is removed from the bottle. The bottle is provided with a collar placed between the body of the bottle and the thread.

These known systems have reduced the quantity of plastic used to produce bottles and caps. However, there is still a margin for improving this aspect and further reducing the quantity of plastic material required to produce each bottle.

Summary of the invention

The invention provides for a container, typically a plastic bottle, for example and in particular for water or other beverages, comprising: a body; a substantially cylindrically shaped end portion or neck, forming an opening mouth; a thread, formed on an external surface of said end portion, for engaging a closing cap. Between the body of the container and the end portion or neck there is provided a guiding shoulder to guide the container in the packaging plants.

In this way the collar or annular ridge normally provided on the neck of the container, between the thread and the body of the container, is omitted. This results in a reduction of the plastic material required to produce the container, both because the neck can be shorter, and because the plastic material forming the projecting collar is no longer necessary.

Advantageously, the end portion or neck of the container extends from the mouth of the container up to said guiding shoulder. Preferably, the shoulder has an external diameter equal to the diameter of the external surface of the end portion or neck of the container and an internal diameter smaller than the external diameter and equal to the minimum diameter of a shoulder connecting the end portion or neck to the body of the container.

According to some embodiments, the thread has at least one stop surface for cooperating with a security element of a closing cap of the container.

According to another aspect, the invention relates to a system comprising a screw cap and a container, typically a bottle, as described above.

According to yet another aspect, the invention relates to a preform for producing a plastic container, typically a bottle, as described above. In some embodiments, the preform comprises a main body and a substantially cylindrical end portion or neck, having a radial dimension greater than the radial dimension of the body of the preform (where radial dimension of the body of the preform is preferably intended as the minimum radial dimension of this body, if it has a variable dimension) and having a thread formed on an external cylindrical surface of the end portion or neck. Between the end portion or neck and the body of the preform there is provided a shoulder intended to form a guiding surface of the container, said shoulder extending radially inward from the substantially cylindrical surface of the end part or neck of the preform.

According to a different aspect, the invention provides for a screw cap for a container comprising a lateral wall and an internal thread formed on an internal surface of the lateral wall, characterized in that the lateral wall comprises a security element configured to be irreversibly altered when the screw cap is removed from the container. The security element is permanently altered, for example deformed or broken, when the cap is unscrewed, as a result of interference with the external thread of the container, for example a bottle. A tamper evident seal is thus obtained without the need to use an additional band on the cap and related collars on the bottle. A reduction of the length or height of the end portion or neck of the bottle of around 6-7 mm, typically around 6.5 mm, is also obtained. In this area, the thickness of the plastic material is around 1 mm. This results in a substantial saving of plastic material, with considerable reduction of costs and environmental impact.

In advantageous embodiments of the cap, the security element is arranged in an intermediate position of the lateral wall, between an end edge and a front wall of the cap. It can have a portion projecting from the internal surface of the lateral wall toward a rotation axis of the cap. For example, the security element can comprise a tab projecting toward the inside of the cap. In advantageous embodiments, the tab extends tangentially and preferably with an inclination corresponding to the inclination of the thread. The tab can be housed in a cutout or slit provided in the lateral wall of the cap and can be fastened at a proximal end thereof to the wall, while the distal end can project toward the internal volume of the cap, so as to interfere with the external thread of the bottle or other container.

Further features and embodiments of the invention are described hereunder and are defined in the appended claims, which form an integral part of the present description.

Features and embodiments are disclosed here below and are further set forth in the appended claims, which form an integral part of the present description. The above brief description sets forth features of the various embodiments of the present invention in order that the detailed description that follows may be better understood and in order that the present contributions to the art may be better appreciated. There are, of course, other features of the invention that will be described hereinafter and which will be set forth in the appended claims. In this respect, before explaining several embodiments of the invention in details, it is understood that the various embodiments of the invention are not limited in their application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception, upon which the disclosure is based, may readily be utilized as a basis for designing other structures, methods, and/or systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

Brief description of the drawinfis

The invention will be better understood by following the description and accompanying drawing, which shows a non-limiting practical embodiment of the invention. More in particular, in the drawing:

Fig.1 shows a side view of the upper part of a bottle with a cap according to the invention;

Fig.2 shows a side view of the cap of Fig. 1 ;

Fig.3 shows a section according to III-III of Fig.2;

Fig.4 shows a side view of the neck of the bottle, with the cap removed;

Fig.5 shows a section according to V-V of Fig.4;

Fig.6 shows a section according to VI- VI of Fig.4, with the addition of the cap applied to close the mouth of the bottle, screwed on and integral;

Fig.7 shows the section of Fig.6 after the cap has been at least partly unscrewed and the security element has been broken;

Fig.8 shows a preform for producing a bottle of the type shown in Fig.4;

Fig.9 shows an improved preform for producing a bottle of the type shown in Fig.4; and

Figs.10 and 11 show sections analogous to the sections of Figs.6 and 7 in a further embodiment.

Detailed description of an embodiment

The following detailed description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Additionally, the drawings are not necessarily drawn to scale. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

Reference throughout the specification to "one embodiment" or "an embodiment" or "some embodiments" means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase "in one embodiment" or "in an embodiment" or "in some embodiments" in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

Hereinafter, specific reference will be made to an embodiment wherein the plastic container is a bottle, for example a bottle for beverages, such as mineral water or the like. However, it must be understood that the concept on which the invention is based can also be embodied in other types of plastic containers with similar requirements and technical-functional characteristics similar to those of bottles for water and/or beverages.

In Fig.l a plastic bottle for water and/or beverages of other type is indicated with 1, while the cap of the bottle, in the closed arrangement, is indicated with 3. The neck or upper end portion of the bottle 1 is indicated with 1 A. The body of the bottle is indicated with IB and the shoulder between neck 1 A and body IB is indicated with I S. Fig.4 shows an enlargement of the neck 1A of the bottle without the cap 3. Around the neck 1A of the bottle 1, below the mouth 1C and on the external cylindrical surface 1Z of the neck 1A, there is formed an external thread 5 that can comprise one or more threads 5A. Each thread can have one or more breaks 5B. In fact, in some embodiments each thread 5 A is discontinuous and broken in one or more points or break areas 5B. On the one hand this enables a reduction in the plastic material required to produce the bottle and on the other it facilitates operation of the security cap, as will be explained below.

More in particular, the bottle 1 has no collar between neck 1 A and body IB of the bottle 1. It has a shoulder I S that joins the main body IB of the bottle to the upper part or neck 1 A, on the external cylindrical surface 1Z of which, having an external diameter DM, the thread 5 is formed.

The cylindrical portion forming the neck 1A of the bottle ends at the bottom with an undercut or shoulder IX, below which the shoulder IS of the bottle is connected. The undercut or shoulder IX forms an annular supporting surface, with a major diameter equal to the diameter DM of the cylindrical portion 1A forming the neck of the bottle and a minor diameter indicated with Dm. The annular shoulder of radial dimension (DM - Dm)/2 thus formed is sufficient to provide a guiding surface for handling the bottle in the filling plants. The shoulder IX formed starting from the external cylindrical surface of the end portion or neck 1A toward the axis of the bottle 1 in substance replaces the collar normally provided on prior art bottles, which projects radially outward with respect to the cylindrical surface on which the thread of the bottle is produced.

The shape of the bottle 1 shown in Fig.4 enables a reduction in the quantity of plastic material required to produce the bottle with respect to conventional solutions. In fact, on the one hand the collar that is usually provided between the thread of the neck of the bottle and the body of the bottle is eliminated. By eliminating the collar, the quantity of plastic required to form it is also eliminated. Moreover, as there is no collar, the axial length of the neck of the bottle can be reduced. The axial length of the portion of neck 1A of the bottle of Fig.4 (between thread 5 and shoulder I S of the bottle) is substantially less (by several millimeters) than the neck of conventional bottles, which are provided with at least one and, in some cases, with two collars.

In some embodiments, the diameter DM and the diameter Dm can be such as to form a shoulder IX with a radial dimension of around 3-4 mm, for example around 3.5 mm. For example, the diameter DM can be in the order of 22-23 mm and the diameter Dm can be in the order of 15-16 mm. The height of the cylindrical portion 1A forming the neck of the bottle can be in the order of 12-20 mm, for example around 15 mm.

This different shape of the upper part of the bottle implies, in conventional bottles for mineral water or beverages, a reduction in weight of around 2-2.5 g per bottle. Modern bottling plants produce several tens of thousands of bottles per hour and therefore a reduction of around 2 grams of plastic on each bottle implies a very large saving of plastic material, with economic advantages for the manufacturer and a reduction of environmental impact. For example, in a bottling plant that produces 80,000 bottles per hour, modification of the upper part of the bottle described above implies a saving of around 160 - 176 kg/hour of plastic, which in a continuous processing plant implies a daily saving of 3840-4224 kg/day of plastic and consequently of 1400-1542 tons/year of plastic. This leads to a corresponding reduction of the quantity of plastic disposed of as waste and/or recycled. With regard to cost, in the case of PET, which currently costs 1,180 Euro per ton, the annual saving is of around 1 ,650,000- 1 ,820,000 Euro.

The cap 3 can generally have an axial- symmetrical shape, with axis A-A. The cap 3 can comprise a lateral wall 7 extending from an end edge or lower edge 9 to a front wall or upper wall 11 of the cap 3. The lateral wall 7 has an external surface 7 A and an internal surface 7B. Along the internal surface 7B an internal thread 13 is provided, which comprises one or more threads 13 A. The internal thread 13 is configured to cooperate with the external thread 5 provided on the neck 1A of the bottle 1.

The height H of the cap 1, i.e. the dimension in axial direction of the cap 3, can advantageously be such that, when the cap 3 is screwed onto the bottle 1, the edge 9 of the cap is approximately positioned at the shoulder IX formed between the cylindrical portion 1A and the shoulder IS of the bottle 1.

Along the extension of the lateral wall 7, i.e. between the edge 9 and the front wall 11 , in the wall 7 there is housed a security element, or tamper evident element, i.e. a member designed to interact with the bottle 1 and indicate whether the bottle has been opened. The security element replaces the conventional security band or tamper evident band provided on prior art caps. In the drawing, the security element is indicated as a whole with 15. In some embodiments, the security or tamper evident element 15 comprises a tab 17 and a cutout or slit 19 formed in the lateral wall 7 and extending for the whole of the thickness thereof, i.e. open on both the internal 7B and external 7A surfaces of the lateral wall 7.

In some embodiments, the tab 17 and the slit or cutout 19 are oriented approximately tangentially, i.e. they have a larger dimension in the circumferential or perimeter direction of the wall 7 and a smaller dimension in the axial direction.

In advantageous embodiments, the tab 17 and the slit or groove 19 are oriented approximately in the direction of the threads 13 A of the internal thread 13. Advantageously, the tab 17 and the respective cutout or slit 19 that houses it are arranged in the groove between two adjacent threads 13 A, as can be seen in particular in Figs.2 and 3. When the cap 3 is screwed onto the neck of the bottle 1 , the tab 17 and the related cutout or slit 19 are thus arranged at a thread 5 A of the external thread 5 of the bottle.

In practice, on the internal face of the cap, the tab 17 can be fully housed in the slit or cutout 19, with the exception of a distal end 17A. In substance, the tab 17 is set back with respect to the internal surface 7B or flush there with, except for the distal end 17 A. The opposite end of the tab 17, labled with 17B and hereinafter named proximal end 17B, is fastened to the material forming the wall 7 of the cap 3. Between the distal end 17A and the proximal end 17B of the tab 17 there extends the main body of the tab 17. The thickness of the body of the tab can correspond substantially to the thickness of the lateral wall 7.

Therefore, in practice in some embodiments the tab 17 is constituted by an elongated portion of the same material forming the wall 7 of the cap 3, joined to the wall 7 at the proximal end 17B, while the remaining part is separated from the wall 7, but housed in the thickness of the lateral wall 7 inside the slit or cutout 19.

The distal end 17A of the tab 17 is generally shaped so as to interfere with the neck of the bottle 1 when it is unscrewed, so as to cause a permanent visible alteration of the tab 17. The shape of the distal end 17A is also such as to enable initial screwing of the cap 3 onto the bottle 1 without deformation or permanent alteration of the tab 17. In this way the tab 17 acts as a security or tamper evident element that indicates if the bottle has been opened, enabling the user to check whether the bottle is integral, for example at the time of purchase.

In some embodiments, along the main body of the tab 17, between the distal end 17A and the proximal end 17B, an incision 17C is provided that forms a preferential bending or breaking point, for purposes that will be explained below. In some embodiments, a second preferential bending or breaking point can be provided at the proximal end 17B of the tab 17, as can be seen in particular in Figs. 6 and 7. The incision 17C can be formed on the external surface of the tab, as shown in the drawing, or on the internal surface thereof. Likewise, an internal or external incision can also be provided at the proximal end 17B of the tab, as shown in the drawing. It would also be possible for both an internal and an external incision to be provided.

In some embodiments, the distal end 17A of the tab 17 has an end surface 17D that extends toward the inside of the cap 3, i.e. toward the axis A-A of said cap, beyond the internal surface 7B of the lateral wall 7. The end surface 17D can be radial, or inclined with respect to the radial direction, as shown in the drawing.

In advantageous embodiments, the innermost corner of the end surface 17D is joined to the body of the tab 17 by means of a second surface 17E facing the inside of the cap 3. In practical embodiments, the connection surface 17E can be curved, or flat, as shown by way of example in Figs. 6 and 7. When the cap is integral (Fig.6) the surface 17E is more inclined than the surface 17D with respect to the radial direction. The connection corner between the two surfaces 17D and 17E projects toward the inside of the cap 3, i.e. beyond the internal surface 7B of the lateral wall 7.

When the cap is screwed onto the bottle, as can be seen in Fig.6, the distal end 17A of the tab 17 projects toward the neck 1 A of the bottle 1 and is inserted in one of the breaks 5B of the external thread 5.

In advantageous embodiments, at least at some of the breaks 5B, the corresponding thread 5A has a stop surface 5C inclined with respect to the radial direction and forming an undercut. As can be seen in particular in Fig.6, the orientation of the front surface 17D of the tab 17 and the orientation of the stop surface 5C of the thread 5 A, at the break 5B of which the distal end 17A of the tab 17 is positioned, are such that when the cap is unscrewed, according to the arrow F (Figs.6, 7), the distal end 17A of the tab 17 abuts in the undercut formed by the stop surface 5C and the rotation of the cap causes outward deformation (arrow fl7, Fig.7) of the tab 17. Deformation is facilitated by the facilitated deformation or breaking point 17C in the central area of the body of the tab and by the facilitated deformation or breaking point at the proximal end 17B of the tab 17, where this joins to the wall 7 of the cap 3.

Rotation of the cap 3 in the direction of unscrewing (arrow F), causes therefore a permanent deformation or breakage of the tab. This condition (Fig.7) is easily detectable from the outside of the bottle and of the cap. The tab 17 thus forms a security or tamper evident element that replaces the conventional tamper evident band. The user is able to determine the integrity of the bottle by observing or touching the tab 17.

The function of security or tamper evident element is obtained without the need to manufacture a tamper evident band along the lower edge 1A of the cap and therefore reducing the quantity of material required to produce the cap. The need for a collar on the bottle, which in prior art bottles has the sole function of cooperating with the tamper evident band, is also eliminated. This also contributes to limiting the quantity of plastic used to produce the bottles.

Fig. 8 schematically shows a preform used to produce the bottle 1. The preform has a body IP, intended to form the body of the bottle, the preformed portion 5P with the external thread 5 and the shoulder IX. The preformed portion 5P constitutes an end portion or neck 1 A, which corresponds to the end portion or neck 1A of the bottle 1. The external surface 1Z of the end portion or neck 1A is substantially cylindrical. The thread 5 projects radially outward from the cylindrical surface 1Z, of the end portion or neck 1A, while the shoulder IX extends radially inward from the lower edge of the external cylindrical surface 1Z, with diameter DM, until reaching the minimum diameter Dm.

In some embodiments, under the shoulder IX the preform has a shape that increases in diameter, to facilitate subsequent molding of the finished bottle.

Fig.9 schematically shows an improved preform for producing a bottle of the type described above. Also in this embodiment, the preform has a body IP, destined to form the body of the bottle, the preformed portion 5P with the external thread 5 and the shoulder IX. The body IP preferably has a constant external diameter from the shoulder IX to the bottom of the preform, indicated with IF. This external diameter is equal to the minor diameter Dm of the shoulder IX of the bottle 1.

In some embodiments the security system of the present invention can be made more efficient by the presence of a breakable constraining element between the tab 17 and the wall 7 of the cap. This additional element is illustrated by way of example in a modified embodiment, shown in Figs.10 and 11, which show sections similar to those of Figs. 6 and 7. The same numbers indicate parts equal or equivalent to those described above. In Figs. 10 and 11, reference 17F indicates a breakable constraining element, which joins the tab 17 to the edge of the cutout or slit 19 formed in the wall 7.

In some embodiments, the element 17F has the form of a bridge and can be formed at the distal end of the tab 17.

When the cap 3 is unscrewed, the deformation of the tab 17 causes tearing of the bridge 17F. This provides the user with an even clearer indication of the fact that the container is not integral.

In some embodiments, the bridge 17F or other breakable element can be placed in a different position, for example along the lateral extension of the tab 17, rather than at the distal end thereof. It would also be possible to provide more than one breakable element, for example more than one bridge 17F, in various points of the tab 17.

The embodiments described above and illustrated in the drawings have been discussed in detail as examples of embodiment of the invention. Those skilled in the art will understand that many modifications, variants, additions and omissions are possible, without departing from the principles, concepts and teachings of the present invention as defined in the appended claims. Therefore, the scope of the invention must be determined purely on the basis of the broadest interpretation of the appended claims, comprising these modifications, variants, additions and omissions therein. The terms "comprise" and its derivatives do not exclude the presence of further elements or steps besides those specifically indicated in a given claim. The term "a" or "an" preceding an element, means or characteristic of a claim does not exclude the presence of a plurality of these elements, means or characteristics. When a device claim lists a plurality of "means", some or all of these "means" can be implemented by a single component, member or structure. The stating of given elements, characteristics or means in distinct dependent claims does not exclude the possibility of said elements, characteristics or means being combined with one another. Any reference numbers in the appended claims are provided to facilitate reading of the claims with reference to the description and to the drawing, and do not limit the scope of protection represented by the claims.

Claims

1. A container comprising: a body (IB); a substantially cylindrically shaped end portion or neck (1A), forming an opening mouth (1C); a thread (5), formed on an external surface (1Z) of said end portion (1A), for engaging a closing cap; characterized in that between the body (IB) of the container and the end portion (1 A) there is provided a guiding shoulder (IX) for guiding the container in packaging plants.

2. The container as claimed in claim 1, wherein said end portion or neck (IX) extends from the mouth (1C) of the container (1) to said guiding shoulder (IX)

3. The container as claimed in claim 1 or 2, wherein said shoulder (IX) has an external diameter (DM) equal to the diameter of the external surface (1Z) of the end portion (1 A) of the container.

4. The container as claimed in claim 3, wherein said shoulder (IX) has an internal diameter (Dm), smaller than the external diameter (DM) and equal to the minimum diameter of a shoulder (IS) connecting the end portion or neck (1 A) to the body (1 B) of the container.

5. The container as claimed in one or more of the preceding claims, wherein said thread (5) has at least one stop surface (5B) to cooperate with a security element (15) of a closing cap (3).

6. A system comprising a container as claimed in one or more of claims 1 to 5, and a screw cap for said container (1), said screw cap (3) comprising a lateral wall (7) and an internal thread (13) formed on an internal surface of the lateral wall (7), wherein said lateral wall comprises a security element (15) configured to be irreversibly altered when the screw cap (3) is removed from the container (1).

7. The system as claimed in claim 6, wherein said security element (15) is arranged in an intermediate position of the lateral wall (7) of the cap (3), between an end edge (9) and a front wall of the cap (11).

8. The system as claimed in claim 6 or 7, wherein said security element (15) is projecting from the internal surface of the lateral wall (7) toward a rotation axis of the cap (3).

9. The system as claimed in one or more of claims 6 to 8, wherein said security element (15) comprises at least one breakable element, which is broken when the cap is unscrewed from the container.

10. The system as claimed in one or more of claims 6 to 9, wherein said security element (15) is configured to interfere with the thread (5) of the container (1) when the cap (3) is unscrewed from the container and suffer permanent deformation visible from the outside of the cap, as a result of interference between security element and container. The system as claimed in one or more of claims 6 to 10, wherein said security element (15) comprises a tab (17) formed in said lateral wall (7) and having a distal end (17A) projecting toward the inside of the lateral wall to cooperate with the thread (5) of the container (1), and wherein said tab (17) preferably comprises: a proximal end, fastened to the lateral wall (7) of the cap (3), opposite said distal end (17A); an intermediate body normally housed in a seat (19) produced in said lateral wall (7), the distal end projecting from said seat toward the inside of the lateral wall (7).

12. The system as claimed in claim 10, wherein said tab extends tangentially along said lateral wall and preferably with an extension substantially parallel to the thread (13) of the cap

13. The system as claimed in one or more of claims 6 to 12, wherein the distal end of the tab has a front surface configured and arranged to abut against a stop surface produced on a thread of the container with which the cap is engaged, when the cap is unscrewed from the container, and wherein the front surface is preferably oriented approximately radially.

14. The system as claimed in one or more of claims 6 to 13, wherein said tab (17) is joined to the lateral wall by at least one breakable element, preferably formed by a bridge (17F) that joins tab to the edge of a cutout or slit (19) produced in said lateral wall (7) and in which the tab is housed.

15. A preform for producing a plastic container according to one or more of claims 1 to 5, comprising a main body (IP) and a substantially cylindrical end portion or neck (1 A), having a radial dimension greater than the radial dimension of the body and having a thread (5) formed on an external cylindrical surface (1Z) of the end portion or neck (1 A); between the end portion or neck (1A) and the body (IP) of the preform there being provided a shoulder (IX) intended to form a guiding surface of the container, said shoulder extending radially inward from the substantially cylindrical surface (1Z) of the end part or neck (1A) of the preform.