WO2014060893A1

WO2014060893A1 - A cap for containers

Info

Publication number: WO2014060893A1
Application number: PCT/IB2013/059058
Authority: WO
Inventors: Alessandro Falzoni
Original assignee: Sacmi Cooperativa Meccanici Imola Societa' Cooperativa
Priority date: 2012-10-18
Filing date: 2013-10-02
Publication date: 2014-04-24
Also published as: IN2015KN00239A; ITMO20120253A1; BR112015003177B1; BR112015003177A2; MX2015002002A

Abstract

A cap for a container comprises: - a side wall (2) provided with at least one anchoring element (3) for removably fixing the cap (1; 101) to a neck (20) of the container; - a top wall (4) arranged transversely to the side wall (2); - a connection zone (5) in which the side wall (2) is connected to the top wall (4). The connection zone (5) comprises a first wall portion (6) which projects from the side wall (2) towards the inside of the cap (1; 101) and a second wall portion (7) which joins the first wall portion (6) to the top wall (4), the first wall portion (6) and the second wall portion (7) defining a recess structure (9) on an outer surface of the connection zone (5).

Description

A cap for containers.

DESCRIPTION

The invention relates to a cap for containers, particularly a cap that is obtainable by moulding a polymeric material. The cap according to the invention is particularly suitable for closing bottles, for example intended to contain liquids, though it can theoretically be used to close other types of containers, for example jars.

Caps for bottles are known, said caps comprising a cylindrical side wall, on an inner surface of which one or more anchoring elements are obtained, for example threads. The anchoring elements are suitable for enabling the cap to be removably fixed to a neck of the bottle. The known caps further comprise a top wall, having a substantially circular plan shape, from which the cylindrical side wall projects.

An inner sealing lip and an outer sealing lip project from the top wall of the known caps towards the inside of the cap. The inner sealing lip and the outer sealing lip both have an annular shape, but the inner sealing lip has a smaller diameter than the outer sealing lip. The inner sealing lip is intended to engage with an inner side surface of the bottle neck, whereas the outer sealing lip is intended to engage with an outer side surface of the bottle neck. In this manner, the inner sealing lip and the outer sealing lip make it difficult, if not impossible, for substances to pass from inside the bottle towards the outside or vice-versa.

Caps provided with two sealing lips of the above-mentioned type are disclosed, for example, in US 4489845, EP0076778 and US 4560077. The caps provided with an inner sealing lip and an outer sealing lip of the above-described type have a number of disadvantages which appear when the bottle neck on which the cap is applied is subjected to temperatures above room temperature. For example, the necks of bottles that are filled by means of hot filling processes can easily reach temperatures of about 70-90°C during the filling and capping steps and in the instants immediately thereafter. Furthermore, during transport from the place of manufacture to the point of sale, it may occur that temperatures of about 40-50°C are reached in the vehicles which transport the filled, closed bottles, particularly in summertime.

At these temperatures, the bottle neck tends to widen as a result both of thermal expansion and the pressure that builds inside the bottle, especially if the bottle contains a carbonated beverage. The cap, which is usually made with materials having a higher percentage of crystalline phase and which are thus more rigid compared to the bottle neck, expands less than the latter. Therefore, the neck of the bottle applies on the cap, and in particular on the outer sealing lip, a force that tends to widen the outer sealing lip circumferentially.

Due to its limited thickness, the outer sealing lip is sometimes not able to withstand the widening force applied by the neck of the bottle. It may thus occur that the outer sealing lip is significantly deformed, so that the sealing capacity thereof is compromised.

Caps are also known which comprise a bead that projects towards the inside of the cap from a connection zone between the cylindrical side wall and the top wall. Caps of this type are described, for example, in EP 0960054 and in EP 0316167. The bead increases stiffness of the connection zone connecting the cylindrical side wall and the top wall and ensures a good resistance to the widening action exerted by the neck of the bottle when the latter expands.

However, the bead of the above-described caps has the disadvantage that, in the connection zone between the cylindrical side wall and the top wall of the cap, the thickness of the cap is relatively great. This implies a significant increase in the amount of polymeric material necessary to manufacture a single cap. Moreover, due to its large thickness, the connection zone between the cylindrical side wall and the top wall may not be easy to cool evenly during moulding of the cap. In addition, the bead may cause the connection zone between the cylindrical side wall and the top wall to become excessively rigid, which would result in difficulties in applying the cap on the bottle, when the bottle has to be sealed after the filling step.

An object of the invention is to improve the caps for closing containers, particularly bottles.

A further object is to provide a cap for containers that is capable of effectively containing any expansion or widening of a container neck on which the cap is applied.

Another object is to provide a cap for containers that does not require an excessive quantity of polymeric material in order to be produced.

Still another object is to provide a cap for containers that can be easily cooled during production of the cap.

A further object is to provide a cap for containers that can be easily applied on filled containers to be sealed.

According to the invention, there is provided a cap for a container, comprising:

a side wall provided with at least one anchoring element for removably fixing the cap to a container neck;

a top wall arranged transversely to the side wall;

a connection zone in which the side wall is connected to the top wall; wherein the connection zone comprises a first wall portion which projects from the side wall towards the inside of the cap and a second wall portion which joins the first wall portion to the top wall, so that the second wall portion can sealingly engage with an outer side surface of the container neck, the first wall portion and the second wall portion defining a recess structure on an outer surface of the connection zone.

In the cap according to the invention, the second wall portion of the connection zone comes into contact with the outer side surface of the container neck, exerting the function that in caps according to the state of the art was exerted by the outer sealing lip. The second wall portion of the connection zone has a greater rigidity than the outer sealing lip of the known caps, which projected as a cantilever beam from the top wall of the cap and was therefore very flexible. On the contrary, in order to deform the second wall portion of the cap according to the invention, it is necessary to compress the first wall portion along a direction in which the first wall portion extends, which requires relatively great effort. Consequently, owing to the conformation of the connection zone, the cap according to the invention is capable of effectively opposing any expansion or swelling of the container neck.

Moreover, the recess structure lightens the connection zone on the cap exterior. This makes it possible to reduce the quantity of material required to form a single cap, compared to known caps provided with a bead in the connection zone.

The recess structure further enables cooling of the cap to be simplified, if the cap is obtained by moulding a polymeric material. Indeed, the recess structure prevents excessive quantities of polymeric material from being concentrated in the connection zone. These excessive quantities would require longer cooling times compared to other zones of the cap.

Finally, the recess structure maintains the rigidity of the connection zone below a threshold beyond which the cap might be applied with difficulty to the filled container to be sealed. At the end of the industrial filling process, the container can thus be capped with ease.

In an embodiment, the recess structure comprises a plurality of recesses distributed circumferentially on the outside of the cap along the connection zone.

The cap can further comprise a plurality of stiffening ribs distributed circumferentially on the outside of the cap along the connection zone. A stiffening rib separates each recess from the adjacent recess.

The stiffening ribs serve to further increase the rigidity of the connection zone, so that the cap is able to resist expansion or swelling of the neck, without reaching, however, levels of rigidity such as to create difficulties when the container must be industrially capped. In an embodiment, an inner sealing lip, having for example an annular conformation, projects from the top wall on the inside of the cap, so as to sealingly engage with an inner side surface of the container neck.

When the cap is applied on a container, the inner sealing lip ensures a good seal in contact with the inner side surface of the container neck. The second wall portion of the connection zone ensures a good seal in contact with the outer side surface of the container neck. It is thus possible to prevent substances from passing between the inside of the container and the outside environment, or vice-versa.

The invention can be better understood and implemented with reference to the appended drawings, which illustrate some example embodiments that do not limit the implementation thereof, in which:

Figure 1 is a view from below of a cap for closing a container;

Figure 2 is a cross section taken along the plane ll-ll of Figure 1 ;

Figure 3 is a cross section taken along the plane Ill-Ill of Figure 2;

Figure 4 is a cross section like the one in Figure 2, showing the cap applied on a container neck;

Figure 5 is a perspective view showing the cap of Figures 1 to 4 from the outside;

Figure 6 is a schematic cross section showing a cap according to an alternative embodiment;

Figure 7 is a view from below of the cap of Figure 6.

Figures 1 to 5 show a cap 1 suitable for being removably fixed to a container in order to close an open end thereof. The container that the cap 1 allows to close can be a bottle intended to contain a liquid, a jar or a container of another type.

The cap 1 is made of polymeric material, for example by moulding. In particular, the cap 1 can be produced by injection or compression moulding, although other production technologies should not be ruled out. The cap 1 comprises a side wall 2, which extends around an axis Z. In the example illustrated, the side wall 2 is substantially cylindrical. When the cap 1 is applied on a container neck, the side wall 2 is substantially vertical.

The side wall 2 is provided, on an inner surface thereof, with one or more anchoring elements 3 which enable the cap 1 to be removably fixed to a neck of the container to be closed. In the example illustrated, the anchoring elements 3 comprise a plurality of thread portions suitable for engaging with corresponding threads formed on the container neck.

In an alternative unillustrated embodiment, the anchoring elements 3 can have a conformation that differs from the thread portions shown in Figures 1 to 5. For example, the anchoring elements 3 could comprise beads or cam elements.

The cap 1 further comprises a transverse wall 4, which is arranged transversely, in particular perpendicularly, to the axis Z. The transverse wall 4 is substantially flat and has a substantially circular shape when seen in a plan view.

When the cap 1 is applied on a container neck, the transverse wall 4 is positioned at a greater height than the side wall 2, so as to close an open upper end of the container. The transverse wall 4 can thus be defined as a top wall of the cap 1 , the adjective "top" referring to the position of the transverse wall 4 during use.

A connection zone 5 is provided to connect the side wall 2 to the transverse wall 4. The connection zone 5 is shown in detail in the enlarged portion of Figure 2.

The connection zone 5 comprises a first wall portion 6 that is tilted relative to the side wall 2 and projects towards the inside of the cap 1 . The first wall portion 6 extends around the axis Z. The first wall portion 6 is arranged transversely relative to the axis Z. The first wall portion 6 projects towards the inside of the cap 1 , i.e. towards the axis Z, from an upper edge area of the side wall 2.

As shown in figure 2, the first wall portion 6 has, on the section plane of figure 2, a conformation substantially plane and straight. In other words, the first wall portion 6 has an overall conical or circular conformation, coaxial to axis Z.

The connection zone 5 further comprises a second wall portion 7, which is interposed between the first wall portion 6 and the transverse wall 4. More particularly, the second wall portion 7 connects the first wall portion 6 to a peripheral edge of the transverse wall 4.

The second wall portion 7 likewise extends around the axis Z.

The second wall portion 7 has a different inclination from the first wall portion 6. In particular, the second wall portion 7 can be less tilted, i.e. arranged in a configuration that is closer to a vertical configuration, compared to the first wall portion 6. The adjective "vertical" is used here with reference to the position that the cap assumes when it is applied on a container, in which the axis Z is substantially vertical and the transverse wall 4 is positioned at a greater height than the side wall 2.

In the example shown, the second wall portion 7 is substantially vertical.

The first wall portion 6 has a thickness that is substantially equal to the thickness of the second wall portion 7.

In the cap according to the present invention, the second wall portion 7 of the connection zone 5 contacts the external lateral surface of the container neck, performing the function which, in known caps, is performed by an external sealing lip. The second wall portion 7 of the connection zone 5 has an higher rigidity than the external sealing lip of known caps, this because of the presence of the first wall portion 6. Actually, in order to deform the second wall portion 7 of the cap according to the invention, it is necessary to compress the first wall portion 6 along the direction of the first wall portion 6. As consequence, thanks to the conformation of the connection zone, the cap according to the invention is able to effectively contrast any dilatation or bulging of the container neck.

The second wall portion 7 is delimited, on the inside of the cap 1 , by a sealing surface 8 suitable for engaging with an outer side surface of the container neck. The sealing surface 8 can be slightly convex towards the inside of the cap 1 , or it can be shaped like a lip which projects towards the inside of the cap 1 , so as to more easily exert a sealing action when the sealing surface 8 comes into contact with the container neck.

The first wall portion 6 and the second wall portion 7 define, on an outer surface of the connection zone 5 - i.e. on a surface of the connection zone 5 turned towards the outside of the cap 1 - a recess structure 9 which enables the connection zone 5 to be made lighter compared to the case where the cap were to be delimited by an external profile of the type adopted in the known caps.

The recess structure 9 lightens the connection zone on the outside of the cap. This allows a reduction of the material necessary for producing a cap, with respect to known caps having a thicker connection zone.

The recess structure 9 allows to ease up the cooling of the cap, in cases wherein the cap is obtained by moulding of a polymeric material. Actually, the recess structure 9 avoids that an excessive polymeric material mass is concentrated in the connection zone, which would require longer cooling time.

Furthermore the recess structure 9 keeps the rigidity of the connection zone 5 behind a threshold value above which the cap could become difficult to be applied on the filled container to be closed. At the end of the industrial filling process, the container can thus be capped easily.

In the example illustrated, the recess structure 9 comprises a plurality of recesses 10 distributed around the axis Z along the connection zone 5, on the outside of the cap 1 . There is further provided a plurality of stiffening ribs 1 1 , which are likewise distributed around the axis Z along the connection zone 5, on the outside of the cap 1 .

In other words, the recesses 10 and the stiffening ribs 1 1 extend along an edge on the outside of the cap 1 , in the connection zone 5 between the side wall 2 and the transverse wall 4.

Each recess 10 is defined between two stiffening ribs 1 1 . In other words, each stiffening rib 1 1 separates two adjacent recesses 10. The stiffening ribs 1 1 have a substantially flat conformation. Each stiffening rib 1 1 extends mainly in a plane that contains the axis Z. The stiffening ribs 1 1 are thus radial ribs.

The stiffening ribs 1 1 have a rounded outside profile.

The stiffening ribs 1 1 have a thickness that is substantially constant between one rib and another, as well as along the individual rib.

The stiffening ribs 1 1 can be equally spaced apart angularly.

The stiffening ribs allow to further improve the rigidity of the connection zone, such that the cap is able to resist dilation or bulging of the container neck, without reaching a rigidity which could create difficulty if the container has to be industrially capped.

The recesses 10 may have an angular extension around the axis Z that is equal between one recess 10 and another.

At the recesses 10, the connection zone 5 has an external profile that substantially copies the internal profile of the connection zone 5, that is, of the first wall portion 6 and the second wall portion 7. In other words, at the recesses 10, the internal profile and external profile of the connection zone 5 have substantially the same conformation, in particular a wavy profile that projects towards the inside of the cap and then joins up, vertically or almost vertically, with the transverse wall 4.

The cap 1 can also be provided with an inner sealing lip 12, of an annular shape, which projects from the transverse wall 4 towards the inside of the cap 1 . The inner sealing lip 12 is suitable for being inserted inside the container neck so as to sealingly engage with the inner side surface of the neck. In particular, the inner sealing lip 12 can be delimited by a convex sealing surface 13 for contacting the inner side surface of the container neck.

When the cap is applied on a container, the inner sealing lip 12 guarantees a good sealing in contact with the inner lateral surface of the container neck. The second wall portion 7 of the connection zone 5 guarantees a good sealing in contact with the outer lateral surface of the container neck. In this way it is possible to prevent any substance exchange between the container inside and the environment, or vice versa.

The cap 1 can comprise an abutment element 16, configured as an annular protrusion that projects from the transverse wall 4 towards the inside of the cap 1 . The abutment element 16 is interposed between the sealing surface 8 and the inner sealing lip 12. In other words, the abutment element 16 has a diameter that is smaller than the diameter of the sealing surface 8, but larger than the diameter of the inner sealing lip 12.

The abutment element 16 is shorter than the inner sealing lip 12, so as to engage with an upper edge of the container neck.

In an embodiment, the abutment element 16 can be omitted.

On an outer surface of the side wall 2, knurls 14 can be present to make it easier both for the cap 1 to be applied on a container in an automatic capping line, and for the user to grip the cap 1 when the cap 1 must be removed from the container or applied on the container.

The knurls 14 can have the form of protruding lines that project from the outer surface of the side wall 2, parallel to the axis Z.

The knurls 14 can also be grouped in groups, two adjacent groups of knurls 14 being separated by a smooth (i.e. not knurled) portion 15 of the outer surface of the side wall 2, as in the example in Figure 5. In the example in Figure 5, the groups of knurls 14 are formed by three knurls

14.

Alternatively, the knurls 14 can be distributed in an equally spaced manner around the axis Z.

The knurls 14 can extend as a continuation, along the side wall 2, of all or part of the stiffening ribs 1 1 . In the latter case, as shown in Figure 5, the stiffening ribs 1 1 from which the knurls 14 extend can project towards the outside of the cap 1 more than the other stiffening ribs 1 1 . The cap 1 can further comprise a tamper evident ring 17, connected in a breakable manner to a lower edge of the side wall 2, for example by means of a plurality of bridge elements.

The tamper evident ring 17 can comprise an outer annular portion 18, connected to the side wall 2 and extending below the latter. The tamper evident ring 17 can further comprise a folded-up portion 19, connected to the outer annular portion 18 and folded up inside the cap 1 , so as to be surrounded by the outer annular portion 18. The folded-up portion 19 is suitable for interacting with an annular protrusion arranged on the outside of the container neck.

The cap 1 can be made of any polymeric material capable of being moulded. In particular, the cap 1 can be made of a polyolefin, in particular high density polyethylene (HDPE).

The polymeric material used to make the cap 1 can have a melt index ranging between 0.2 and 10 g/10 minutes, measured at 2.16 kg - 190°C according to ISO 1 133 or equivalent standards.

The density thereof can range between 952 and 964 kg/m³, measured according to the ISO 1 183 or equivalent standards.

The material of the cap 1 can have a single-mode or multimodal molecular weight distribution.

In an embodiment, the material of the cap 1 is a homopolymer.

Alternatively, the material of the cap 1 can be a copolymer of ethylene and another -olefin having a number of carbon atoms ranging from 3 to 12. Figure 4 shows a configuration in which the cap 1 is applied on a container neck 20. In this configuration, the sealing surface 8 of the second wall portion 7 in the connection zone 5 is in contact with an outer side surface 21 of the neck 20.

The inner sealing lip 12 is arranged inside the neck 20, in such a way that the convex sealing surface 13 is in contact with an inner side surface 22 of the neck 20. A top edge 23 of the neck 20 abuts against the abutment element 16, which, if present, assures that the neck 20 has penetrated into the cap 1 by the correct amount.

The sealing surface 8 and the convex sealing surface 13 prevent any substances present inside the container, particularly gaseous ones, from leaking into the outside environment and at the same time they prevent the substances present in the outside environment from entering the container. The integrity and properties of the liquid or other substance present in the container are thus preserved.

Moreover, if the neck 20 tends to widen, due for example to high temperatures or the pressure that is generated inside the container, the neck 20 applies to the cap 1 , in the connection zone 5, a force that is radially directed outwards relative to the axis Z.

The cap 1 reacts with a force directed along the first wall portion 6 of the connection zone 5, in the direction indicated by the arrow F in Figure 4. In order to deform the cap 1 outwardly, the neck 20 must overcome the force indicated by the arrow F.

The first wall portion 6 locally behaves like a beam that must be axially compressed in order for the neck 20 to widen. Therefore, the neck 20 can widen only after overcoming a considerable resistant force. In most cases, the neck 20 is not able to overcome this resistant force and thus remains substantially undeformed.

In practice, the outer sealing ring present in the caps according to the state of the art has been replaced in the cap 1 by the sealing surface 8 of the second wall portion 7. For the reasons set out above, the second wall portion 7 is more difficult to deform compared to the outer sealing ring of the known caps. Therefore, the cap 1 is capable of more effectively limiting the deformations of the neck.

At the same time, the recesses 10 enable the cap 1 to be made lighter along an outer edge in which the side wall 2 is joined to the transverse wall 4. In this way, when the cap is applied onto the neck 20 of the container at the end of the industrial container filling process, the connection zone 5 does not behave in an excessively rigid manner and does not create excessive difficulties during the capping step.

In the example described thus far, the first wall portion 6 forms an obtuse angle with the side wall 2 of the cap 1 . In particular, the angle formed between the first wall portion 6 and the side wall 2 can range between 90° and 150°.

In an unillustrated embodiment, the first wall portion 6 could form a 90° angle with the side wall 2. In this case, the first wall portion 6 would project towards the inside of the cap 1 , perpendicularly to the side wall 2.

Alternatively, the first wall portion 6 could form an acute angle, that is, of less than 90°, with the side wall 2. In this case, the first wall portion 6 would extend towards the inside of the cap 1 in such a way as to be inclined downwards, i.e. toward the tamper evident ring 17.

Figures 6 and 7 illustrate an alternative embodiment of a cap 101 for closing a container.

The cap 101 differs from the cap 1 shown in Figures 1 to 5 because it is provided with a stiffening structure to stiffen the transverse wall 4. The stiffening structure comprises a rib arrangement 24, which project from an inner surface of the transverse wall 4 towards the inside of the cap 101 . In particular, the rib arrangement 24 comprises a plurality of radial ribs 25 which extend from a central zone towards the inner sealing lip 12. The radial ribs 25 can have a height which, after having remained constant for an initial portion, progressively decreases, coming nearer to the inner sealing lip 12.

The rib arrangement 24 can further comprise an annular rib 26 arranged in a central region of the transverse wall 4. The annular rib 26 can have a circular shape when seen in a plan view and can be concentric to the transverse wall 4. The radial ribs 25 start from the annular rib 26 and extend radially outwards from the latter. In an embodiment, it is possible to provide five radial ribs 25, but more in general the number of radial ribs 25 can be freely chosen and can be other than five.

The radial ribs 25 give the rib arrangement 24 a star-like configuration. In an unillustrated embodiment, instead of the radial ribs 25 it is possible to adopt a plurality of ribs that extend over the transverse wall 4 in non- radial directions. It is also possible to omit the annular rib 26.

The rib arrangement 24 enables the rigidity of the transverse wall 4 to be increased so as to limit the deformations of the transverse wall 4, especially when high pressures build up inside of the container closed by the cap 101 . This can occur frequently, especially in the case of containers containing carbonated beverages.

The other features of the cap 101 are analogous to those previously described for the cap 1 .

In particular, the cap 101 comprises a connection zone 5 shaped similarly to the connection zone 5 described with reference to Figures 1 to 5 and exhibiting the same advantages as previously discussed for the cap 1 . In the connection zone 5 it is possible to identify the first wall portion 6 and the second wall portion 7, shaped as previously described with reference to Figures 1 to 5. The cap 101 moreover has, on an outer surface of the connection zone 5, the previously described stiffening ribs 1 1 and recesses 10.

Claims

1. A cap for a container, comprising:

a side wall (2) provided with at least one anchoring element (3) for removably fixing the cap (1 ; 101 ) to a neck (20) of the container;

a top wall (4) arranged transversely to the side wall (2); a connection zone (5) in which the side wall (2) is connected to the top wall (4);

wherein the connection zone (5) comprises a first wall portion (6) which projects from the side wall (2) towards the inside of the cap (1 ; 101 ) and a second wall portion (7) which joins the first wall portion (6) to the top wall (4), the first wall portion (6) and the second wall portion (7) defining a recess structure (9) on an outer surface of the connection zone (5);

characterised in that the first wall portion (6) is plane and straight.

2. Cap according to claim 1 , wherein the first wall portion (6) has a thickness substantially equal to the thickness of the second wall portion (7).

3. A cap according to claim 1 , wherein the second wall portion (7) comprises a sealing surface (8) suitable for sealingly engaging with an outer side surface (22) of the neck (20), the first wall portion (6) supporting the second wall portion (7) in such a manner that, in order to widen the diameter of the sealing surface (8), it is necessary to compress the first wall portion (6) in a radial direction relative to the side wall (2).

4. A cap according to claim 1 or 2, wherein the first wall portion (6) is tilted relative to the side wall (2).

5. A cap according to any preceding claim, wherein the first wall portion (6) forms an angle with the side wall (2) which is greater than or equal to 90°, and less than or equal to 150°.

6. A cap according to any preceding claim, wherein the second wall portion (7) is substantially parallel to the side wall (2).

7. Cap according to one of the preceding claims, wherein the first wall portion (6) and the second wall portion (7) define, on an outer surface of the connection zone (5), a recess structure (9).

8. A cap according to any preceding claim, wherein the recess structure (9) comprises a plurality of recesses (10) distributed along the outer surface of the connection zone (5), a plurality of stiffening ribs (1 1 ) being provided along said outer surface in such a manner that each recess (10) is defined between two consecutive stiffening ribs (1 1 ).

9. A cap according to claim 6, wherein each stiffening rib (1 1 ) has a flat conformation and extends radially relative to the side wall (4).

10. A cap according to claim 6 or 7, wherein, at each recess (10), the first wall portion (6) and the second wall portion (7) have substantially the same thickness.

11. A cap according to any preceding claim, wherein an inner sealing lip (12) having an annular conformation projects from the top wall (4) for engaging with an inner side surface (22) of the neck (20).

12. A cap according to any preceding claim, and further comprising an annular abutment element (16) that projects from the top wall (4) so that a top edge (23) of the neck (20) can abut against the annular abutment element (16).