WO2004050496A1

WO2004050496A1 - Plastics cap

Info

Publication number: WO2004050496A1
Application number: PCT/IT2002/000753
Authority: WO
Inventors: Alfonso Caruana
Original assignee: Gefit S.P.A.
Priority date: 2002-11-29
Filing date: 2002-11-29
Publication date: 2004-06-17
Also published as: AU2002359966A1

Abstract

The present invention relates to a plastics cap (1) comprising a skirt (2) which extends cylindrically about an axis (X-X) of the cap, a top (3), a connecting region (4), between the skirt and the top, having a first inner portion (10) for joining to the top, a second inner portion (11) for joining to the skirt and an intermediate inner portion (12) between the first portion and the second portion, and a safety ring (5), characterized in that it comprises an annular lip (17) placed in a position such that it interferes with the surface of the outer wall (23) of the edge (21) of the mouth of a container when the cap is screwed onto the container, the annular lip (17) being completely contained within the intermediate portion (12) of the connecting region (4).

Description

DESCRIPTION "PLASTICS CAP"

The present invention relates to a plastics cap comprising a skirt having an internal thread, a top, a connecting region between the skirt and the top and a safety ring. In particular, the invention relates to a plastics cap having a seal formed in a unitary manner on the inner wall of the cap.

It is known that various types of plastics cap for containers are currently on the market.

A particular type of cap consists in a body formed by a skirt, a top, a connecting region between the skirt and the top, a safety ring and by a seal joined to the top by melting the contact surfaces between the top and the seal, in which the seal extends internally and radially on the top of the cap with its outer edge to the extent that it leaves a portion of the connecting region uncovered, as described in international patent application PCT/ITOO/00171 belonging to the same applicant .

That type of cap has given good results from the point of view of leaktightness, above all in cases where it is fitted on containers holding carbonated liquids.

Leaktightness is ensured owing to the provision of the uncovered portion of the connecting region, which portion enables the outer edge of the seal to be resiliently deformed, expanding in the radial direction in response to the pressing exerted by the upper edge of the neck of a bottle when the cap is screwed onto the bottle. This expansion enables the seal to adhere better to the upper edge of the neck of the bottle.

Despite the good results obtained with carbonated liquids, the above-mentioned type of plastics cap having a seal nevertheless has its limitations in respect of leaktightness under conditions in which pressure is particularly high.

It has been observed that if the pressure inside a container reaches values higher than 7 bar, the top of the cap, and the seal which is fixedly joined thereto, tends to bulge in a very visible manner. Since the leaktightness has been produced, as stated above, precisely by the engagement between the seal and the upper edge of the neck of the container at the level of the top of the cap, the bulging brings about a movement of the seal away from the edge of the neck of the container sufficient to cause a dangerous reduction in the efficacy of the leaktightness.

Consequently, a great need is felt to provide a plastics cap which solves the problems of the prior art as regards leaktightness under high pressure. The problem underlying the present invention is therefore to provide a plastics cap which has structural and functional characteristics such as to satisfy the above-mentioned requirements and at the same time to avoid the disadvantages exhibited by prior art plastics caps having a seal

The problem is solved in accordance with the appended claims .

Further characteristics and advantages of the plastics cap according to the present invention will emerge from the following description of some of its preferred embodiments which are given by way of non- limiting example with reference to the appended drawings, in which: - Figure 1 is a sectional view of a plastics cap having a seal according to the invention;

- Figure 2 is a sectional view of the plastics cap of Figure 1 screwed onto a neck of a bottle in section;

- Figure 3 is a sectional view of a plastics cap having a seal according to the invention in accordance with a first variant thereof;

- Figure 4 is a sectional view of a plastics cap having a seal according to the invention in accordance with a second variant thereof; - Figure 5 is a sectional view of a plastics cap according to the invention in accordance with a third variant thereof;

- Figure 6 is a view from below of the section along the line VI-VI of the cap of Figure 1. Referring to Figure 1, 1 generally indicates a plastics cap having a seal according to the present invention.

The cap 1 comprises a skirt 2 , a top 3 , a connecting region 4 between the skirt and the top, a safety ring 5 and a seal 6.

The skirt 2, which extends cylindrically about an axis X-X of the cap, has an inner wall having a single- start thread 7 and an outer wall having knurling 8 for facilitating the operations of screwing and unscrewing the cap 1 onto and from the neck of a bottle (not shown) .

In particular, the knurling 8 is created by numerous ribs disposed longitudinally relative to the outer wall of the skirt 2 in such a manner as to extend substantially over the entire length thereof.

The top 3 is a substantially flat disc connected to the skirt 2 by means of the connecting region . Preferably, the top has a diameter of 26 mm ± 0.5.

The connecting region 4 is in the form of a ring provided with an inner surface 9 and an outer surface 90. The inner surface 9 comprises a first portion 10 for joining to the top 3 of the cap, a second portion 11 for joining to the skirt 2 of the cap and a third portion 12 which is intermediate between the first joining portion 10 and the second joining portion 11.

The first portion 10 is substantially curved while the second portion 11 is placed substantially at right- angles relative to the skirt 2 of the cap in order to form a shoulder. In particular, the first portion 10 may be otherwise regarded as that portion which in Figure 1 is traversed by an imaginary straight line Y-Y parallel with the axis X-X of the cap 1. In other words, with reference to Figure 6, the first portion 10 is represented by a circular ring which circumscribes the top 3 of the cap and which contains the straight line Y- Y.

The second portion 11 is joined to the intermediate portion 12 forming a corner. Preferably, the second portion 11 has a length in cross-section of 0.5 mm ± 0.5.

The intermediate portion 12 is frustoconical and is inclined relative to the axis X-X of the cap in such a manner as to form with the top 3 an angle greater than 90°, preferably an angle of 120°, and, with the second portion 11, an angle greater than 90°, preferably an angle of 240°. Preferably, the intermediate portion has a length in cross-section of 2 mm ± 0.5.

According to the explanation just given, with reference to Figure 6, the intermediate portion 12 is also in the form of a circular ring which circumscribes the first portion 10, while the second portion 11 is in the form of another circular ring which in turn circumscribes the intermediate portion 12. The safety ring 5 comprises an annular raised portion 13 facing the inside. The annular raised portion 13, by engaging with a corresponding annular projection 13a provided at the base of the neck of a bottle as represented in Figure 2, acts as a stop means for holding the tamper-evident ring 5 on the neck of the bottle.

In addition, the tamper-evident ring 5 has bridges 14 for joining to the skirt 2 of the cap 1. The bridges are intended to break when the bottle is first opened. The seal 6 is in the form of a thin ring which extends to cover a peripheral portion 15 of the top 3 of the cap and all of the portion 10 for joining to the top and the intermediate portion 12 of the connecting region 4. In the particular embodiment illustrated in Figure 1, the seal 6 has a downwardly projecting inner annular lip 16 - which is to be arranged at the location of the inner wall of the upper edge of the container - and an outer annular lip 17. The outer annular lip 17 is placed at the location of the intermediate portion 12 of the inner surface 9 of the connecting region 4.

According to what has just been described, the inner annular lip 16 and the outer annular lip 17 delimit a seat 18 suitable for receiving by interference the upper edge of the neck of a container, as will be better described with reference to Figure 2.

In other words, it may be stated that the outer annular lip 17 is positioned externally with respect to the above-mentioned imaginary straight line Y-Y which is parallel with the axis X-X and extends across the portion 10 for joining to the top 3. Consequently, the outer annular lip 17 is never crossed by the above- mentioned straight line Y-Y.

With reference to Figure 2, a brief description will now be given of the functioning of the plastics cap having a seal according to the present invention.

When the cap 1 is screwed onto the neck 20, for example, of a bottle (not shown) into the closing position, the upper edge 21 of the neck is pressed against the seal 6 and received entirely in its seat 18. In addition, the inner annular lip 16 and the outer annular lip 17 so arranged enable the above-mentioned upper edge 21 to be completely surrounded, along with the inner surface 22 and the outer surface 23 of the neck 20 which are located in the vicinity of that edge.

The main advantage afforded by the cap according to the invention derives from the provision of at least one intermediate portion 12 of the connecting region 4 between the top 3 and the skirt 2, which portion is substantially flat and inclined relative to the axis X-X and which is positioned externally with respect to the joining portion 10 between the top 3 and the connecting region 4 and from which the outer annular lip 17 of the seal 6 extends . It has been observed that, as a result of very high pressures which may occur inside a container with the structure of the cap 1 just described, the above- mentioned bulging of the top 3 of the cap 1 creates a lever effect with the connecting region 4, the fulcrum of which is represented by the joining portion 10 between the top 3 and the connecting region 4. Owing to the lever effect, therefore, the connecting region 4 tends to be bent towards the inside of the cap. This bending in turn tends to push the outer annular lip 17 against the outer surface 23 of the neck 20 of a container, promoting the leaktightness of the cap.

Another advantage afforded by the plastics cap just described resides in the fact that the intermediate portion 12 of the connecting region 4 forms a kind of abutment against which the seal is held when the upper edge 21 and the corresponding outer surface 23 of the neck 20 of a container are fitted thereon, as described, above .

In particular, experiments have shown that the cap 1 is able to withstand internal pressures of up to 17 bar.

Preferably, the inner annular lip 16 may have an undercut (not shown) on its outer wall to which corresponds a projection suitable for defining a point of sealing by interference against the inner surface 22 of the neck 20 of a container. Thus, leaktightness against the escape of the liquid contained in the container is increased.

The advantages mentioned above are particularly appreciated in cases where the containers on which the caps of the invention are fitted remain for a relatively long time stored and/or subjected to a relatively high temperature and contain highly carbonated liquids. A typical case is represented by plastics bottles containing highly carbonated beverages, such as, for example, cola, lemonade or the like.

However, it should be noted that the plastics cap according to the present invention can also be used to close containers in general, such as jars and cans for preserves .

In that case, it is important to form a seal, for example, after the pasteurisation of the foodstuffs contained in the containers.

Referring to Figure 3, 101 generally indicates a plastics cap having a seal according to a first variant of the present invention.

The cap 101 comprises a skirt 102, a top 103, a connecting region 104 between the skirt and the top, a safety ring 105 and a seal 106. The skirt 102, the top 103 and the safety ring 105 are identical to the skirt 2, the top 3 and the safety ring 5 of the previous embodiment and they will therefore not be described further here.

The connecting region 104 is in the form of a ring having an inner surface 109 and an outer surface 190 and the inner surface 109 of which is inclined relative to the axis X-X and preferably has a length in cross- section of 2.8 mm ± 0.5.

In particular, the inner surface 109 comprises a first portion 110 for joining to the top 103 of the cap, a second portion 111 for joining to the skirt 102 of the cap and a third portion 112 which is intermediate between the first joining portion 110 and the second joining portion 111. The first coupling portion 110 and the second coupling portion 111 form with the top 103 and with the skirt 102, respectively, angles of a size greater than 90°, preferably of 120°.

The intermediate portion 112 is substantially flat and inclined relative to the axis X-X, with respect to which it forms an angle of 60°.

The seal 106 is in the form of a thin ring which extends to cover a peripheral portion 115 of the top 103 of the cap 101, all of the joining portion 110 between the top and the connecting region and some of the intermediate portion 112, leaving uncovered a region 120 thereof which is next to the portion 111 for joining to the skirt 102.

The uncovered region 120 preferably corresponds substantially to half the extent of the intermediate portion 112 of the connecting region 104.

In particular, the seal 106 is provided with an inner annular lip 116, facing downwards, which extends from the peripheral portion 115 of the top, substantially parallel with the axis X-X. The outer annular lip 117, on the other hand, faces the outside of the cap 101 and extends from the third portion 112 of the inner surface 109 of the connecting region 104, likewise substantially parallel with the axis X-X of the cap.

In other words, it may be stated that the outer annular lip 117 is placed outside with respect to an imaginary straight line Y-Y disposed parallel with the axis X-X and extending across the first joining portion 110 of the inner surface 109 of the connecting region 104. Furthermore, the same comments as those made previously with reference to Figure 6 apply in this case too.

As for the previous embodiment, the inner annular lip 116 and the outer annular lip 117 delimit a seat 118 suitable for receiving by interference the upper edge of v, the neck of a container (which are not shown) .

It should be noted that, in addition to the effect mentioned above, the region 120 enables the outer lip 117 to be deformed resiliently, expanding in the radial direction in response to the pressing exerted by the upper edge of the neck of a bottle when the cap 104 is screwed onto it. The resilient deformation has the function of causing the seal to adhere better to the upper edge of the neck of the bottle and to the outer surface. located in the vicinity thereof.

This particular embodiment is better suited to conditions where it is more important to provide leaktightness against the escape of liquid rather than against very high pressures inside the container.

With reference to Figure 4, a description will now be given of a second variant of the invention.

The cap 201 comprises a skirt 202, a top 203, a connecting region 204 between the skirt and the top, a safety ring 205 and a seal 206.

The skirt 202, the top 203 and the safety ring 205 will not be described hereinafter because they correspond to those already described above with reference to Figure 3. The connecting region 204 is in the form of a ring which has an inner surface 209 and an outer surface 290 and in which the inner surface is inclined relative to the axis X-X and has a length in cross-section of 2.8 mm

± 0.5. In particular, the inner surface comprises a first portion 210 for joining to the top 203 of the cap, a second portion 211 for joining to the skirt 202 of the cap and a third portion 212 which is intermediate between the first joining portion 210 and the second joining portion 211. The first joining portion 210 and the second joining portion 211 form with the top 203 and with the skirt 202, respectively, angles of a size greater than 90°, preferably 120°. The intermediate portion 212 is substantially flat and inclined relative to the axis X-X, preferably by an angle of 60°.

In particular, with reference to the detail of Figure 4, the intermediate portion 212 has an annular raised portion 224 substantially in the form of a step. The outer surface 290 of the connecting region 204 is traversed by an annular groove 225 which is aligned vertically with the projection 224 and which has the same shape in cross-section. The seal 206 is in the form of a thin ring which extends to cover a peripheral portion 215 of the top 203 of the cap 201, all of the joining portion 210 between the top and the connecting region and some of the intermediate portion 212 between the first portion 210 and the second portion 211, leaving a region 220 thereof uncovered.

The uncovered region 220 preferably corresponds substantially to half the extent of the intermediate portion 212 of the connecting region 204. In particular, the seal 206 is provided with an inner annular lip 216 which faces downwards and which extends from the peripheral portion 215 of the top 203, substantially parallel with the axis X-X. The outer annular lip 217, on the other hand, extends from the intermediate portion 212 of the inner surface 209 of the connecting region 204 at the location of the projection 224 in a direction substantially parallel with the axis X-X of the cap.

In other words, it may be stated that the outer annular lip 217 is placed externally with respect to an imaginary straight line Y-Y located parallel with the axis X-X and crossing the first portion 210 coupling the connecting region 204 to the top 203. In addition, the same comments as those made above with reference to Figure 6 apply in this case too.

As in the case of the previous embodiment, the inner annular lip 216 and the outer annular lip 217 delimit a seat 218 suitable for receiving by interference the upper edge of the neck of a container (which are not shown) .

It should be noted that, in addition to the above- mentioned lever effect and to the ability of the outer lip 217 to be deformed resiliently, expanding in the radial direction in response to the pressing exerted by the upper edge of the neck of a bottle when the cap 204 is screwed onto it, the annular raised portion 224 permits the creation of a kind of shoulder suitable for forming a stop for the base of the seal 206.

Consequently, the above-mentioned embodiment presents itself as an intermediate solution between the previous two embodiments .

According to yet another variant of the invention, the top of the cap may also have a plurality of anchoring elements (not shown) facing the inside of the cap and disposed along a circumference positioned in the vicinity of the connecting region.

Those anchoring elements may have, for example, a dove-tailed cross-sectional shape.

The seal will then have recessed undercuts suitable for producing a form-fit with the projecting undercuts defined by the dove-tailed cross-sectional shape of the anchoring elements.

Thus, the co-operation of the anchoring elements with the corresponding recessed undercuts of the seal ensures the secure coupling of the seal to the top of the cap even against torsions to which the seal may be subjected when the upper edge of a bottle engages with it when the cap is screwed on.

According to a further variant of the invention (not shown) , an annular tooth may be provided between the inner annular lip and the outer annular lip of the seal. This annular tooth has the function of creating a point of greater leaktightness if the surface of the upper edge of the neck of the bottle is uneven. The plastics cap having a seal according to the present invention may be produced by adapting a normal mould of the well-known rotary type.

The rotary moulds currently used for the production of plastics caps having a seal comprise a fixed plate having a series of moulding cavities, or female mould portions, which is generally subdivided into one half having cavities suitable for moulding the seal and one half having cavities suitable for moulding the cap proper . Injectors for the injection of thermoplastic material which has been rendered fluid are also coupled, by way of suitable holes, to the moulding cavities of the fixed plate.

The mould also comprises a rotary plate having a series of cores, or male portions, suitable for being inserted into and for closing all of the respective moulding cavities assigned either to the moulding of the seals or to the moulding of the cap.

Consequently, the fixed plate and the rotary plate will be arranged in such a manner that they fit together and permit the above-mentioned insertion of the cores into the moulding cavities.

In particular, in order to produce the caps having a seal according to the present invention, the head end portion of the male portions is modified in such a manner that it has an outer annular upper surface suitable for abutting, and therefore sealing, the connecting region between the base and the lateral walls of the cavities for moulding the seal . As regards the moulding of the annular seal, it is sufficient merely to provide a mould having two coaxial male portions, of which the outer portion has an annular upper surface, as described above, suitable for abutting the connecting region between the base and the lateral walls of the cavities for moulding the seal. The inner male portion, on the other hand, has an upper surface such as to form an abutment on the base of the moulding cavity during the stage of moulding the seal.

Thus, an annular chamber is formed in which the material for forming the seal is injected.

In a first stage of the process for moulding the cap having a seal according to the present invention, the rotary plate is moved close to the fixed plate in such a manner that the head portions of the cores each enter a cavity for moulding either the seal or the cap. In particular, at the location of the cavities for moulding the seal, the cores are positioned in abutment with the connecting region between the base and the lateral walls of the cavities by way of the above- mentioned upper annular surface.

As a result, the injection of thermoplastic material for forming the seal takes place only in the cavity for moulding the seal .

Once the seal has been moulded, the mould is opened, thus enabling the cores to come out of the respective cavities. In particular, the cores coming out of the cavities for moulding the seal carry the moulded seals on their end portion.

Subsequently, the rotary plate, that is to say, the plate carrying the cores, rotates through 180° relative to an axis disposed perpendicularly to its surface of engagement with the fixed plate.

Consequently, the cores with the seal positioned on their head end are at the location of the cavities for moulding the cap, while the cores not carrying any seal on their head end are at the location of the cavities for moulding the seal.

At this point, the rotary plate is again moved close to the fixed plate and the cores carrying the seals enter the cavities for moulding the cap, delimiting a closed moulding chamber for the formation of the cap proper, while the cores without a seal enter the cavities for moulding the seal, as described above, for the formation of the seal . It is now possible to inject thermoplastic material both into the interior of the cavities for moulding the seal and into the interior of the cavities for moulding the cap.

It will be appreciated that, in the portion of the fixed plate carrying the cavities for moulding the seal, again only the seals are moulded while, in the portion of the plate carrying the cavities for moulding the cap, the caps proper are moulded directly around the seals already moulded. Finally, the mould is opened to release the finished cap from the cores coming out of the cavities for moulding the cap.

A further rotation of the rotary plate through 180° enables the mould to return to the initial state and to commence a second moulding cycle.

For the moulding of the anchoring elements according to the variant of the present invention, the base of the moulding cavity has a circular projection having a dove-tailed cross-section suitable for creating, during the stage of forming the seal, the recessed undercut in the thickness of the seal and subsequently, during the stage of forming the cap, the anchoring elements and the depressions in the top of the cap. The stages of forming the cap having an annular seal are identical to those described above.

Alternatively, the plastics cap of the invention may be produced by means of a known bi-injection process, such as, for example, that described in International Patent Application PCT/lTOO/00172 of the same applicant.

In summary, the above-mentioned process makes available a mould in which the formation of the seal and of the cap takes place in the same moulding chamber owing to the positioning of the above-described core inside the chamber in such a manner as to form first a moulding chamber for the seal and then a moulding chamber for the cap.

The plastics cap having a seal according to the present invention may be varied in form according to contingent requirements.

For example, the annular seal may be formed entirely on the inner surface of the connecting region between the top and the skirt . Thus, the bulging effect of the top would influence the seal and, therefore, the leaktightness of the cap only very slightly.

Otherwise, the seal may extend to such a degree that it covers the entire inner surface bf the top of the cap and not just the peripheral portion thereof.

The seal seat which receives the upper edge of the neck of a container may comprise a thickened portion suitable for adaptation to any unevenness on that edge . The anchoring elements may be provided on the seal in such a manner that their projecting undercuts mate with respective recessed undercuts formed in the thickness of the top of the cap.

In that case, the base of the moulding cavity will be modified in such a manner that it has a circular hole having a dove-tailed shape in order to be able to produce this variant.

The thread may have one start or also several starts, depending on the type of bottle neck to which it has to be fitted. The anchoring elements may vary in number and may be in any desired form or they may constitute a continuous ring.

The plastics materials constituting the cap and the seal may vary according to requirements. For example, the cap may be moulded from polypropylene while the seal may be moulded from low-density polyethylene.

Figure 5 shows a third variant of the present invention in which the cap 301 has an inner profile and an outer profile which are substantially identical to those of the cap 1 as described above and shown in

Figure 1.

The cap 301 comprises a skirt 302, a top 303, a connecting region 304 between the skirt and the top and a safety ring 305. The skirt 302 and the safety ring 305 correspond to those already described with reference to the embodiment of Figure 1 and they will therefore not be described further here .

In particular, the top 303 comprises a peripheral portion 315 of its inner surface from which extends an inner annular lip 316 moulded integrally with the top in such a manner as to extend towards the inside of the cap and substantially parallel with the axis X-X of the cap. The inner annular lip 316 is in a form substantially identical to the inner annular lip described and represented with reference to Figure 1.

The inner annular lip 316 is joined to a first joining portion 310 of the connecting region 304 by way of a substantially rectilinear portion 320 which is perpendicular to the axis X-X. The first portion 310 is concave and is in turn joined to a second portion 311 having a rectilinear profile arranged substantially perpendicularly relative to the axis X-X of the cap 301 by way of an intermediate convex third portion 312. According to what has been described and shown in Figure 5, the third portion 312 forms a kind of outer annular lip 317 which is substantially identical to the outer annular lip 17 described with reference to Figure 1 but which is produced integrally with the connecting region 304.

In addition, the inner annular lip 316 and the outer annular lip 317 delimit a seat 318 identical to the seat 18 of Figure 1 suitable for receiving the upper edge of the neck of a container. As explained above, in this case too, the portion 312 is positioned on the outside with respect to an imaginary straight line Y-Y passing through the first joining portion 310 of the connecting region 304, that is to say, the portion which joins the top 303 to the connecting region 304. In addition, the same comments as those made above with reference to Figure 6 apply in this case too.

Thus, as a result of the formation of high pressures which may develop inside a container closed by the cap, the top of the cap is subjected to a force which has its reaction in the connecting region 304 and, because the first portion 310 of the connecting region acts as a fulcrum, it undergoes bending towards the inside . Consequently, in this case too, a lever effect develops which tends to push the outer annular lip 317 against the outer surface of the neck of a container which is in the vicinity of the upper edge thereof.

It follows from this that leaktightness is at any rate increased compared with any plastics cap of the prior art of unitary construction.

As may be appreciated from the above description, the cap having a seal according to the invention enables the requirements referred to in the introductory portion of the present description to be met and at the same time enables the disadvantages exhibited by the prior art caps having a seal to be overcome.

The present invention in fact takes the form of a cap for containers which is simple and functional, particularly in specific conditions such as high pressures of the contents of bottles.

It will be appreciated that a person skilled in the art, in order to satisfy contingent and specific requirements, may introduce numerous modifications and variants to the cap having a seal described above, but they would all be within the scope of the invention as defined by the following claims.

Claims

1. A plastics cap (1; 101; 201; 301) comprising a skirt (2; 102; 202; 302) which extends cylindrically around an axis (X-X) of the cap, a top (3; 103; 203; 303), a connecting region (4; 104; 204; 304), between the skirt and the top, having a first inner portion (10; 110; 210; 310) for joining to the top, a second inner portion (11; 111; 211; 311) for joining to the skirt and an intermediate inner portion (12; 112; 212; 312) between the first portion and the second portion, and a safety ring (5; 105; 205; 305), characterized in that it comprises an annular lip (17; 117; 217; 317) placed in a position such that it interferes with the surface of the outer wall (23) of the edge (21) of the mouth of a container when the cap is screwed onto the container, the annular lip (17; 117; 217; 317) being completely contained within the intermediate portion (12; 112; 212; 312) of the connecting region (4; 104; 204; 304).

2. A plastics cap (1; 101; 201; 301) according to claim 1, also comprising a further annular lip (16; 116;

216; 316) inscribed relative to the annular lip (17; 117; 217; 317) and suitable for delimiting with the latter a seat (18; 118; 218; 318) for sealing engagement with the edge (21) of the mouth of the container.

3. A plastics cap (1; 101; 201) according to claim 1 or 2, wherein the intermediate portion (12; 112; 212) is inclined relative to the axis (X-X) of the cap in order to form with the top (3; 103; 203) an angle greater than 90°.

4. A plastics cap (1; 101; 201) according to claim 3, wherein the angle is 120°.

5. A plastics cap (1) according to any one of claims 1 to 4, comprising a seal (6) which is fixedly joined to the top (3) and which extends to cover a peripheral portion (15) of the top (3) and all of the first joining portion (10) and the intermediate portion (12).

6. A plastics cap (1) according to claim 5, wherein the further annular lip (16) and the annular lip (17) are part of the seal (6) .

7. A plastics cap (101; 201) according to any one of claims 1 to 4, comprising a seal (106; 206) which is fixedly joined to the top (103; 203) and which extends to cover a peripheral portion (115; 215) of the top (103; 203), all of the first portion (110; 210) and some of the intermediate portion (112; 212), leaving a region (120; 220) uncovered.

8. A plastics cap (201) according to claim 7, also comprising an annular raised portion (224) formed at the level of the intermediate portion (212) .

9. A plastics cap (1; 101; 201) according to any one of claims 5 to 8, wherein the seal (6; 106; 206) extends to form a ring.

10. A plastics cap (101; 201) according to any one of claims 7 to 9, wherein the uncovered region (120;

220) of the connecting region (104; 204) corresponds substantially to half the extent of the connecting region.

11. A plastics cap (1; 101; 201; 301) according to any one of claims 2 to 10, wherein the further annular lip (16; 116; 216; 316) comprises on its outer lateral wall an undercut to which corresponds a projection for forming a point of sealing by interference with the inside of the mouth of a container.

12. A plastics cap (1; 101; 201) according to any one of claims 5 to 11, comprising anchoring means for anchoring the seal (6; 106; 206) to the top (3; 103; 203) .

13. A plastics cap (1; 101; 201) according to claim 12, wherein the anchoring means comprise at least one projection formed in a single piece with the top of the cap, the at least one projection having projecting undercuts which produce a form-fit with corresponding recessed undercuts of the seal.

14. A plastics cap (1; 101; 201) according to claim 13, wherein the at least one projection has a dove-tailed cross-section.

15. A plastics cap (1; 101; 201; 301) according to any one of claims 5 to 14, wherein the seal (6; 106; 206) extends from the centre of the top (3; 103; 203) of the cap in such a manner as to form a substantially uniform solid disc.

16. A plastics cap (301) according to claim 1 or 2, wherein the further annular lip (316) and the annular lip (317) are formed integrally with the top (303) and with the connecting region (304) , respectively.