Background of the invention

[0001] The invention relates to a crown closure, in particular a hermetic closure that is usable for sealing a mouth of a container like, for example a bottle, containing pressurized liquids like for example fizzy beverages.

[0002] The invention further relates to a moulding apparatus, in particular a moulding die, to make a crown closure.

[0003] Specifically, but not exclusively, the invention relates to a crown closure for containers made of a metal material and provided with a corrugated skirt wall, in which the closure is applied to an upper mouth of a container by a plugging device that presses the corrugated skirt wall in a radial direction to the neck of the container, to make an undercut coupling to prevent the crown closure from separating from the neck.

[0004] Patent publications US 2018/0370692 Al, US 2010/0326949 Al, US 2005/0199576 Al, US 2005/0029218 Al, US 2001/0035390 Al, US 6,164,472, US 5,458,253 and US 3,229,842 show some examples of crown closures that are usable for sealing the upper mouth of a container.

[0005] Various aspects of prior art crown closures, as well as the moulds used to make the crown closures, are improvable.

[0006] Firstly, it is desirable to make a crown closure that, although it is moulded from a relatively thin metal sheet, is still able to withstand relatively high pressure inside the container.

[0007] It is desirable to provide a crown closure distinguished by great flexibility features to facilitate plugging operations and resistance features to maintain the container hermetically sealed.

Summary of the invention

[0008] One object of the invention is to make a closure that is able to overcome one or more of the aforesaid limits and drawbacks of the prior art.

[0009] One object of the invention is to provide a crown closure that is alternative to those of the prior art.

[0010] One object of the invention is to make a moulding apparatus available for forming a crown closure that is alternative to prior art moulding apparatuses.

[0011] One object of the invention is to provide a moulding apparatus for forming a crown closure that is able to overcome one or more of the aforesaid limits and drawbacks of the prior art.

[0012] In one embodiment, a moulding apparatus comprises a punch and a die with a cavity for moulding a metal shell of a crown closure along a moulding axis, with an odd number N of recesses arranged circumferentially around the moulding axis to form corrugations of a corrugated skirt wall of the crown closure, said die comprising an outer part with a number N of teeth and an internal part with a number N of sectors each of which is arranged in a space comprised between two adjacent teeth, the outer part and the internal part being axially movable with respect to one another such that each sector can adopt a final position during moulding in which it is moved axially in the entry direction of the punch with respect to an initial position, so as to enable a smooth skirt wall of the crown closure to be formed by a process of drawing a cylindrical or pseudo-cylindrical portion of a smooth skirt wall of the crown closure.

[0013] Each sector is in particular so configured that a movement from the initial position to the final position comprises an axial movement that is concordant with an axial entry movement of the punch in the cavity.

Brief description of the drawings

[0014] The invention can be better understood and implemented with reference to the enclosed drawings that illustrate one embodiment thereof by way of non-limiting example, in which:

Figure 1 is a section in vertical elevation of one embodiment, made according to the present invention, of a moulding apparatus that is usable for forming a crown closure, in an open configuration;

Figure 2 is a section in vertical elevation of the moulding apparatus of Figure 1, in a closed moulding configuration;

Figure 3 shows an enlarged detail of Figure 1;

Figure 4 shows an enlarged detail of Figure 2;

Figures 5 and 6 are two perspective views of a part of the die that forms the moulding apparatus of Figure 1, in two different operating configurations;

Figure 7 is a hemisection in vertical elevation of a first embodiment of a crown closure made with the moulding apparatus in Figure 1;

Figure 8 shows an enlarged detail of Figure 7; Figure 9 is a partial section in vertical elevation of a second embodiment of a crown closure made with the moulding apparatus in Figure 1;

Figure 10 is a partial section in a vertical elevation of a third embodiment of a crown closure made with the moulding apparatus in Figure 1;

Figure 11 is a perspective view of a fourth embodiment of a crown closure made with the moulding apparatus in Figure 1;

Figure 12 shows, on the left, a top plan view of the closure in Figure 11 and, on the right, an enlarged detail of the left view;

Figure 13 is a meridian section of the metal shell with which the crown closure in Figure 11 is made;

Figure 14 is an enlargement of a detail in Figure 13;

Figure 15 is a perspective view of a fifth embodiment of a crown closure made with the moulding apparatus in Figure 1;

Figure 16 shows, on the left, a top plan view of the closure in Figure 15 and, on the right, an enlarged detail of the left view;

Figure 17 is a meridian section of the metal shell with which the crown closure in Figure 15 is made;

Figure 18 is an enlargement of a detail in Figure 17.

Detailed description

[0015] With reference to the aforementioned figures, with 1 a moulding apparatus for moulding a crown closure T has been indicated overall.

[0016] The moulding apparatus 1 may comprise, in particular, a die 2 (in this embodiment a lower half mould) for moulding a crown closure T. The moulding apparatus 1 may comprise, in particular, a punch 3 (in this embodiment an upper half mould) for moulding the crown closure T in cooperation with the die 2.

[0017] The die 2 may comprise, in particular, a die body 4 that may define, in particular, at least one suitable cavity for moulding a metal shell of the crown closure T along a moulding axis X.

[0018] The cavity may comprise, in particular, an open side (in this embodiment, an upper side of the cavity) to enable the punch 3 to enter the moulding cavity in an entry direction along the moulding axis X. In this embodiment, the punch 3 enters the moulding cavity vertically from top to bottom. [0019] The die body 3 may define, in particular, a number N of recesses arranged circumferentially around the moulding axis X to form a number N of corrugations of a corrugated skirt wall of the metal shell of the crown closure T. The corrugations comprise, in particular, a series of protrusions W arranged circumferentially and alternating with recesses so as to form the crown of the crown closure. The shape of each corrugation may be, in particular, the same as the conformation of the other corrugations. The number N may be, in particular, an odd number lower than 21, or an odd number lower than 19, or an odd number lower than 17. In one specific embodiment, the number N may be equal to 15. In other embodiments, the number N may be equal to 17, or equal to 19, or equal to 13.

[0020] The die body 4 may comprise, in particular, at least one (fixed) outer part of a body 5 and at least one (movable) internal part of a body 6.

[0021] The outer part of a body 5 may comprise, in particular, a number N (i.e. the same number N of recesses on the die body 4 and of corrugations of the corrugated skirt wall of the metal shell of the crown closure T) of teeth 7 protruding radially inside, where “radially” means with reference to the moulding axis X, and “internal” means with reference to the moulding cavity. In particular, the teeth 7 protrude radially to the moulding axis X that passes substantially to the centre of the moulding cavity. The aforesaid N recesses on the die body 4, arranged for forming N corrugations on the metal shell, are defined in the spaces N comprised between the teeth 7, as will be explained better below.

[0022] The internal part of a body 6 may comprise, in particular, a number N of sectors 8 extending axially, where “axially” is intended with reference to the moulding axis X. Each sector 8 may be, in particular, arranged in a space comprised between two adjacent teeth 7 of the outer part of a body 5. The sectors 8 are arranged and shaped inside respective spaces between the teeth 7 so as to leave the aforesaid N recesses defined that are configured to form N corrugations on the metal shell.

[0023] The outer part of a body 5 and the internal part of a body 6 may be, in particular, movable axially with respect to one another (in particular the outer part of a body 5 may be fixed and the internal part of a body 6 may be movable) such that the sectors 8 and the teeth 7 are movable axially with respect to one another. In particular, it is possible for each sector 8 to be configured to adopt, during moulding (in particular during reciprocal axial movement between punch 3 and die 2) an initial position (see Figure 5, where this initial position is, in particular, an upper position) and a final position (see Figure 6, where this final position is, in particular, a lower position).

[0024] In particular, it is possible for each sector 8 in the final position to be moved axially (i.e. in a direction parallel to the moulding axis X), with respect to the initial position, in the entry direction of the punch 3 in the cavity of the die 2. This entry direction may be, as in the specific embodiment, a vertical downward direction.

[0025] The die 2 may comprise, in particular, a core 9 arranged at least partially inside the cavity of the die 2. The core 9 may be, in particular, arranged in the centre of the cavity. The core 9 may be configured, in particular, for collaborating with the punch 3 in the plastic deformation of the metal sheet in order to form the metal shell of the crown closure T.

[0026] The core 9 may be, in particular, shaped and arranged so as to be able to adopt a non-interaction position (see in particular the position in Figure 3), in which the core 9 does not interact axially with the internal part of a body 6 and can start to receive an axial thrust from the punch 3 (that moves to enter the cavity during moulding).

[0027] The core 9 may be, in particular, movable axially with respect to the die body 4 with the possibility of adopting an initial interaction position, in which the core 9, starting from the aforesaid non interaction position and pushed by the punch 3 that continues the axial movement thereof, meets axially the internal part of a body 6 (against an axial abutting surface arranged on the internal part of a body 6) with the sectors arranged in the initial position.

[0028] The core 9 may be, in particular, shaped and arranged so as to perform an initial axial stroke in which, starting from the aforesaid non-interaction position, the core 9 does not interact in axial contact with the internal part of a body 6, i.e. an initial approach stroke to the abutting surface of the internal part of a body 6.

[0029] The core 9 may be, in particular, movable axially with respect to the die body 4 (in particular with respect to the outer part of a body 5) with the possibility of adopting a final interaction position (see in particular Figure 4), in which the core 9, after the axial meeting with the internal part of a body 6 and still pushed by the punch 3, which still continues its axial position, has moved axially (downwards) the internal part of a body 6 such that each sector 8 is moved from the aforesaid initial position to the aforesaid final position (see Figures 4 and 6).

[0030] The die 2 may comprise, in particular, at each sector 8, an axial recess 10 that is bounded radially internally by an external surface of an end portion of the respective sector 8 (at least when the sector 8 is in the initial position). The recess 10 may be, in particular, bounded circumferentially on two opposite sides by the two teeth 7 between which the respective sector 8 is arranged. The recess 10 may be, in particular, bounded radially externally by an internal surface of a portion of the outer part of a body 5.

[0031] The outer part of a body 5 may comprise, in particular, an annular portion 11 configured so as to have an abutting surface for a blank holder that is suitable for drawing and that belongs to the moulding apparatus 1. The aforesaid abutting surface may be, in particular, couplable with a tubular element 12 that surrounds the punch 3 and is configured to perform a drawing blank holder function during forming of the crown closure T.

[0032] The tubular element 12 may perform, in particular, the function of a shearing element for shearing the metal sheet. Further, as already said, the tubular element 12 may perform, in particular, the function of blank holder element. The tubular element 12 with blank holder function may be associated operationally with elastic means Ml arranged, in particular, to exert an elastic axial force to facilitate the function of blank holder in the moulding step. It is nevertheless possible for the tubular element 12 not to perform the function of blank holder element, or to perform the function of shearing element without also performing the function of blank holder element.

[0033] In the case of the absence of the blank holder function, it is possible, in particular, for the tubular element 12 to be fixed and thus not be slidable axially with respect to the rest of the punch 3. In this case, it is possible, in particular, for the absence of elastic means Ml (for example, the elastic means Ml could be replaced with a stiff spacer in the form of a bush or the tubular element 12 could be constructed integrally with an upper part of the punch).

[0034] In the case of the absence of the function of blank holder, it is possible, in particular, for the die 2 and the punch 3 to be so configured that between the tubular element 12 and the outer part of a body 5 (which is the fixed part of the knurled or corrugated portion) a distance, or gap remains (considered in an axial direction) when the punch 3 reaches the closed position within the die 2 at the end of the punching at the final interaction position (see Figure 4, so that the tubular element 12 will not come to abut or come into contact against the outer part of a body 5). [0035] This distance, or gap, between the shearing part of the punch and the fixed knurled or corrugated part of the die may be defined, in particular, as a result of the fitting heights of the various components and of the corresponding tolerances.

[0036] This distance, or gap, between the shearing part of the punch and the fixed knurled or corrugated part of the die may be defined, in particular, by the use of spacer means D (for example an annular spacer) specifically configured to define the aforesaid distance, or gap. The spacer means D may be arranged, in particular, between the tubular element 14 and the core 9.

[0037] In order to reach, in operating conditions, the distance, or gap, of a desired size (axial dimension) it is possible to run one or more preliminary moulding tests and then choose the spacer means D of the axial dimension that is appropriate to the purpose of obtaining in fact the distance, or gap, of a desired size.

[0038] The desired size of the aforesaid distance, or gap, may be, in particular, equal to the thickness of the metal sheet used, or may be slightly greater than the thickness of the metal sheet used, for example greater than 0.01 millimetres, or 0.02 millimetres, or 0.03 millimetres, or 0.04 millimetres, or 0.05 millimetres. In particular, the desired size of the aforesaid distance, or gap, may be greater than the thickness of the metal sheet used by an amount that is not greater than 0.05 millimetres.

[0039] In general, the moulding apparatuses are of multi-mould type, so that it is possible to run an initial calibration procedure in which preliminary moulding is carried out (for example with a lead pad inserted into each die), after which, if the deformations caused by the preliminary moulding lead to noncompliant products (the test may be in particular conducted by measuring the thicknesses of the products obtained), the thickness of the respective spacer means D is adjusted accordingly.

[0040] The internal part of a body 6 may comprise, in particular, an annular portion 13 that is integral with the circumferential arrangement of the N sectors 8 and from which the aforesaid sectors 8 emerge axially. This annular portion 13 may be, in particular, coupled (for example by a screw coupling, visible in Figures 5 and 6) with a tubular element 14 that has a portion with an abutting surface against which the core 9 comes to abut to push axially the internal part of a body 6 downwards. The core 9 may be, in particular, slidable axially inside the tubular element 14.

[0041] The die 2 may comprise, in particular, a liner 15 that surrounds the outer part of a body 5 and to which the outer part of a body 5 may be fixed. The tubular element 14 that carries the internal part of a body 6 may be, in particular, slidable axially inside the liner 15.

[0042] It is possible, as in the illustrated embodiment, for the axial movement of the internal part of a body 6 to be caused actively by the axial movement of the punch 3, that, after an initial stroke, interacts with the tubular element 14 (with interposing of the core 9 and the spacer means D) and starts to push downwards the internal part of a body 6 (movable part of the knurled or corrugated portion). In particular, the axial dimension, or thickness, of the spacer means D determines the moment at which the axial movement of the internal part of a body 6 starts.

[0043] It is possible, in particular, to regulate a dimension of the moulded product (in particular the dimension indicated by h2, as will be explained better below in the description with reference to Figure 7) on the basis of the axial dimensions, or thickness, of the spacer means D, i.e. by varying substantially the moment at which the axial movement of the internal part of a body 6 starts.

[0044] It is nevertheless possible to provide other embodiments in which the aforesaid active control of the axial movement of the internal part of a body 6 by the axial movement of the punch 3 is absent. Substantially, this active control is not strictly necessary, as in these other embodiments it is the metal sheet that comes into contact with the internal part of a body 6 and drags the internal part of the body 6 downwards. In this case it is possible, in particular, not to provide the spacer means D.

[0045] In this case it is possible, in particular, for there to be elastic means M2 arranged in the die 2 and configured, in particular, to exert an axial elastic force on the internal part of a body 6. The elastic means M2 (spring) may be arranged, in particular, to operate on the tubular element 14. In this case, the height h2 of the moulded product is adjusted by the preloading and the stiffness of the elastic means M2, thereby increasing the stiffness of the elastic means M2 will decrease the height h2, whereas decreasing the stiffness of the elastic means M2 will increase the height h2. The core 9 may perform an ejecting function at the end of moulding. It is observed that the elastic means M2 may be arranged also in embodiments that include the spacer means D (as in the illustrated embodiment) and that the core 9 may perform the function of ejector of the moulded product also in other embodiments (as in the illustrated embodiment). [0046] As said, the moulding apparatus 1 is used to form a crown closure and comprises the die 2 and the punch 3, where the punch 3 is configured to interact during moulding with the internal part of a body 6 so as to move the sectors 8 from the initial position to the final position.

[0047] In Figure 8, a crown closure T is shown that may be made with the moulding apparatus 1. The crown closure T is shown before being applied to a container to seal the container.

[0048] The crown closure T may comprise, in particular, a metal shell 21 with an upper wall 22 configured to close an upper mouth of the container. The metal shell 21 may be made, in particular, of a metal sheet with a thickness of less than 0.18 millimetres, or less than 0.19 millimetres. The metal shell 21 may be made, in particular, of a metal sheet with a thickness comprised between 0.12 and 0.18 millimetres, in particular comprised between 0.14 and 0.16 millimetres. The metal shell 21 may be made, in particular, of a metal sheet with a thickness of less than 0.17 millimetres, in particular less than 0.16 millimetres.

[0049] The metal shell 21 may be made, in particular, of a so-called “blackplate” metal sheet, or steel sheet or cold -rolled metal sheet, or clad metal sheet or stainless steel or aluminium metal sheet or of yet other materials.

[0050] In the illustrated embodiment, the metal shell 21 is made of tinplate, blackplate or chrome strip, with thicknesses of 0.17 millimetres, or 0.16 millimetres, or 0.15 millimetres, or 0.14 millimetres, or 0.13 millimetres. It is possible to provide other nominal thicknesses like, for example, thicknesses with values of 0.005 millimetres more or less than the values cited above.

[0051] The crown closure T may comprise, in particular, a smooth skirt wall 23 configured to surround at least partially a neck of the container (see Figure 7). The crown closure T may comprise, in particular, a curved annular wall 24 that connects the smooth skirt wall 23 to the upper wall 22. The crown closure T may comprise, in particular, a corrugated skirt wall 25 that is joined to the smooth skirt wall 23 and is configured to be folded inwardly when the crown closure T is applied to the container to close the container, so as to engage an annular undercut arranged on the neck of the container.

[0052] The curved annular wall 24 may, in particular, extend outwardly (with outward convexity) and downwardly from a circular perimeter of the upper wall 22. The aforesaid circular perimeter may have, in particular, a diameter comprised between 24 and 28 millimetres.

[0053] The smooth skirt wall 23 may comprise, in particular, a cylindrical or pseudo- cylindrical portion, where “pseudo-cylindrical” means that the deviation from a cylindrical shape is relatively reduced. In particular, a maximum deviation from the cylindrical shape of the aforesaid cylindrical or pseudo-cylindrical portion may be such that the difference between the maximum internal diameter and the minimum internal diameter is less than 0.5 millimetres, or less than 0.4 millimetres, or less than 0.3 millimetres, or less than 0.2 millimetres. In particular, the aforesaid cylindrical or pseudo-cylindrical portion may have an internal diameter comprised between 27 and 31 millimetres. The aforesaid cylindrical or pseudo-cylindrical portion may have, in particular, a vertical dimension that is greater than 0.3 millimetres, or greater than 0.4 millimetres, or greater than 0.5 millimetres, or greater than 0.6 millimetres.

[0054] The aforesaid cylindrical or pseudo-cylindrical portion may be made, in particular, by a drawing process that may occur, in particular, in the moulding apparatus 1 owing to the aforesaid possibility of reciprocal movement between the outer part of a body 5 and the internal part of a body 6.

[0055] In practice, the moulding apparatus 1 disclosed above, in particular owing to the features of the die 2, enables a sort of combined forming to be performed, i.e. in which both forming by moulding a metal sheet with plastic deformation of the material that takes the shape of the cavity of the die 2 by the compression imposed by the punch 3 occurs, and forming occurs by drawing a metal sheet that gives rise to the formation of the cylindrical or pseudo-cylindrical portion through the effect of the thrust of the punch and of the axial movement of the internal part of a body 6. Drawing may be, moreover, promoted by the action of a blank holder (tubular element 12).

[0056] The corrugated skirt wall 25 may extend, in particular, downwardly and outwardly from a lower annular end edge of the smooth skirt wall 23, in particular of the cylindrical or pseudo-cylindrical portion. The corrugated skirt wall 25, as said, comprises the aforesaid number N of corrugations arranged circumferentially and consisting of protrusions W alternating with recesses.

[0057] The crown closure T may be in particular so shaped that a vertical distance hl (see Figure 7) between the upper point of the upper wall 22 (in the embodiment in Figure 7 this upper point is the central point of the upper wall 22, i.e. the intersection point between the axis Y of the closure and the upper surface of the upper wall 22) and the lower end edge of the smooth skirt wall 23 (or of the cylindrical or pseudo-cylindrical portion) is less than 4.5 millimetres, in particular comprised between 3.5 millimetres and 4.0 millimetres. The lower end edge of the smooth skirt wall 23 is, essentially, the circumferential border zone between the smooth skirt wall 23 and the corrugated skirt wall 25.

[0058] The crown closure T may be in particular so shaped that a maximum vertical dimension h2 (see Figure 7) of the corrugated skirt wall 25 is less than 3.0 millimetres, in particular comprised between 2.0 millimetres and 2.5 millimetres.

[0059] The crown closure T may be in particular so shaped that a vertical distance h3 (see Figure 7) between the seal circumference of the lower surface of the upper wall 22 and the lower end edge of the smooth skirt wall 23 is less than 4.0 millimetres, in particular comprised between 3.0 millimetres and 3.5 millimetres, where the aforesaid seal circumference is defined as the circumference intended to be, once the crown closure T is applied to the container, at the vertical cylinder that passes through the circumference placed at the extreme summit of the upper edge of the neck of the container.

[0060] The aforesaid seal circumference can correspond to the border circumference between the upper wall 22 and the curved annular wall 24 (i.e. to the aforementioned circular perimeter of the upper wall 22) or may be slightly less than the aforesaid border circumference, for example less with a diameter difference comprised between 0.1 millimetres and 1.0 millimetres. The aforesaid seal circumference may have, in particular, a diameter comprised between 24 and 27 millimetres.

[0061] The crown closure T may be in particular so shaped that the aforesaid distance hl is greater than the aforesaid dimension h2. In particular, it is possible for the difference hl - h2 between the aforesaid distance hl and the aforesaid dimension h2 to be greater than 1.0 millimetres, in particular comprised between 1.0 millimetres and 2.0 millimetres. The crown closure T may be in particular so shaped that the aforesaid distance h3 is greater than the aforesaid dimension h2. In particular, it is possible for the difference h3 - h2 between the aforesaid distance h3 and the aforesaid dimension h2 to be greater than 0.5 millimetres, in particular comprised between 0.5 millimetres andl.5 millimetres.

[0062] The crown closure T may comprise, in particular, seal means 26 arranged on an internal side of the upper wall 22 to make a seal on the upper mouth of the container after the crown closure T has been applied to the container to seal the container. The seal means 26 may comprise, in particular, an annular seal (for example with a circumferential throat in the centre as in the embodiment in figure 7) set up for interacting in contact with the upper edge of the neck of the container.

[0063] It is possible for a layer of the seal material with which the seal means 26 is made to be arranged on the internal surface of the upper wall 22 in the central space bounded inside the annual washer, in particular so as to cover the entire internal surface of the upper wall 22 in the aforesaid space inside the annular washer, or it is possible not to apply any layer of the seal material to the aforesaid internal surface of the upper wall 22 in the space inside the annular washer so as to reduce the quantity of material used.

[0064] Part of the seal means 26 may be arranged, in particular, on an internal side of the curved annular wall 24.

[0065] The seal means 26 may be applied, in particular, by overmoulding directly on the closure, or it is possible to form a washer (for example a ring) separately (for example by moulding) and then apply the washer after forming the closure. The seal means 26 may be made, in particular, of plastics, of elastomeric material, or cellulose-based material or of still other materials.

[0066] In Figures 9 and 10, two examples of crown closures are shown partially that differ from the embodiment of Figures 7 and 8 only through the particular shape of the upper closing wall 22 closing the container, which in these examples comprises at least one lowering 27 or shallow extending over at least one part of the surface of the upper closing wall 22. In Figures 9 and 10, the seal means 26 is not shown, which could be arranged, in particular, at the curved annular wall 24. In particular, the seal means could be arranged more outside the lowered zone 27. The lowering 27 may have an annular crown shape (in particular a circular crown shape as in the embodiment in Figure 9). The lowering 27 may have a full disk shape extending over the entire area comprised inside the step 28 (in particular a form of circular disk as in the embodiment in Figure 10).

[0067] The upper wall 22 may comprise, in particular, a step 28 that divides the upper wall 22 into an outer portion and an internal portion. The step 28 may descend inwards, i.e. from the outer portion to the internal portion.

[0068] The upper wall 22 may comprise, in particular, another step 29 (see embodiment in Figure 9) arranged further inside the step 28 that may descend outwards, i.e. descending from a more internal portion of the wall to a more external portion of the wall.

[0069] In particular, the lowering 27 of annular shape of the embodiment in Figure 9 is defined between the (more external) step 28 and the other (more internal) step 29, whereas the solid lowering 27 of the embodiment in Figure 10 is defined entirely in the space inside the sole step 28.

[0070] Both for step 28, and for the other step 29 (if present), it is possible for the step to have a minimum height greater than 0.3 millimetres, or greater than 0.5 millimetres, or greater than 0.8 millimetres. Both for step 28, and for the other step 29 (if present), it is possible for the step to extend with a form of circumference, or with other forms, for example a polygonal shape, a (“flower”) undulated shape, a star shape, etc.

[0071] The lowering 27 may have, in particular, a maximum diameter greater than 10 millimetres, or greater than 12 millimetres, or greater than 14 millimetres, or greater than 16 millimetres, or greater than 18 millimetres, or greater than 20 millimetres.

[0072] In order to make a lowering 27, for example as in Figures 9 or 10. it is possible to set up the moulding apparatus 1 in Figure 1 so as to replace the punch 3 and/or the die 2 with a punch and/or a die shaped in a manner corresponding to the shape of the desired lowering 27.

[0073] In use, after the container has been closed by the crown closure in question (for all the embodiments disclosed above), the pressure inside the container pushes the crown closure upwards. This entails generating a radial force that tends to widen the crown closure with risk of loss of the hermetic seal.

[0074] It has been found that a lowering 27 improves some features of the crown closure. In particular, it has been found that, in use (when the crown closure is applied to the container for a hermetic seal closure), the pressure inside the container closed by the crown closure generates, in addition to an undesired lifting of the closure (as in the crown closures of the prior art), also a sort of rotation of the metal shell of the closure around the edge of the upper mouth of the container, precisely by virtue of the presence of the lowering 27. This rotation tends to increase the grip of the crown closure on the neck of the container, promoting the hermetic seal even if the thickness of the metal sheet is minimal.

[0075] As said, the smooth skirt wall 23, which is arranged above the corrugated skirt wall 25, consists of or comprises, a cylindrical or pseudo-cylindrical portion (for all the embodiments disclosed above), may be made by cylindrical drawing on a diameter very near the minimum possible diameter to enable the cylindrical or pseudo-cylindrical portion to come onto the collar of the bottle, in particular with an internal diameter of the cylindrical or pseudo-cylindrical portion substantially the same as an outer diameter of the annular ridge (or neck ring) that protrudes from the neck of the container and that enables the aforesaid undercut to be formed.

[0076] Further, the corrugated skirt wall 25 may have a relatively reduced vertical dimension, whereas a part of the skirt wall of the closure, with a non-insignificant vertical or height dimension, instead of having corrugations, is made like a tapered portion (cylindrical or almost cylindrical) with an internal diameter as near as possible to the minimum for being placed on the neck of the container.

[0077] Owing to the crown closure in question (for all the embodiments disclosed above), the corrugated skirt wall 25 is relatively inflexible through the effect of the radial component of the force generated by the force generated by the pressure inside the container. The crown closure in question (for all the embodiments disclosed above) further enables a relatively very deep and adhesive undercut to be made.

[0078] It has in fact been found that in use (closure applied to the container), the cylindrical or pseudo-cylindrical portion (in particular, drawn) of the smooth skirt wall 23 contributes to deformation of the closure (due, for example, to the pressure inside the container generated by the gas in a gaseous beverage) less than the corrugated skirt wall 25.

[0079] In particular, it has been found that the various corrugations or folds formed by the succession of protrusions W and recesses folded inwards to engage the undercut on the neck of the container, through the effect of the pressure inside the container substantially tend to relax to the original shape whereas the cylindrical or pseudo-cylindrical portion enables the deformation to be reduced and ensures an effective hermetic seal also over a long time.

[0080] The moulding apparatus 1 disclosed above advantageously enables the aforesaid cylindrical or pseudo-cylindrical portion to be made and at the same time enables, again advantageously, the corrugated skirt wall 25 to be made by compression moulding that is anyway significantly effective, by the punch 3 and the die 2, i.e. with a male half mould and a female half mould that are complementary to one another that force the material (metal sheet) to take on a preset shape defined between the two half moulds.

[0081] This enables, for example, the difference in height or depth between the protrusions W and the recesses that form the corrugations to be accentuated. Further, this can promote the possibility of accentuating the engagement of the corrugated skirt wall 25 with the undercut on the neck of the container, increasing the engaged surface and/or the capacity to retain on the neck of the container.

[0082] Further, the moulding apparatus 1 promotes the formation on the corrugated skirt wall 25 of folds (alternation of protrusions W and recesses) with narrower three- dimensional curvatures, with the possibility of giving greater resistance to the engagement of the closure and less deformation.

[0083] It has been found that making closures with a number N of corrugations that is odd, in particular less than twenty, or nineteen or seventeen, for example equal to fifteen, or thirteen, or eleven, reduces the risk of deformations (in particular, ovalization) of the closure applied to the container during conveying.

[0084] The seal means of the closures may comprise, in particular, seal devices like, for example, claddings or washers. Such seal devices may be, in particular, moulded from a single type of plastic or may be made of a compound of different plastics or may have a multilayered structure. The seal device (for example the polymer washer) may be made of LDPE, LLDPE, ULDPE, mixtures of similar products, EVA, PVC-based compounds, etc. Alternatively, it is possible to use thermoplastic elastomers and mixtures thereof, for example combinations of polyolefins and styrene block copolymers, or combinations of hard polymer and elastomers (for example PP/EPR or PP/EPDM). The density of the polymer (or of the mixtures) may be, in particular, comprised between 0.87 and 0.94 g/cm ³ , in particular between 0.88 and 0.92 g/cm ³ . The hardness of the material may be, in particular, comprised between 40 and 90 shore A, for example between 55 and 85 shore A. [0085] The closures, in particular the metal shell of the closures, may be made, for example, of materials that, especially on the basis of the mechanical properties thereof, may belong to the classes included in the interval from TH520 to TH650, in particular in the classes TH520, TH550, TH580, TH620, TH650 (according to European standard EN 10202 for packaging products or according to standard AMFCE) or in the classes included in the interval DR 7.5 to DR 9.5, in particular in the classes DR 7.5, DR 8.0, DR 8.5, DR 9.0, DR 9.5 (according to standard ASTM 623 for rolling mill products). These materials may be used, in particular, in combination with thicknesses below 0.18 millimetres, for example thicknesses comprised between 0.13 and 0.18 millimetres.

[0086] Each protrusion W comprises an external surface and an internal surface. The external surface of each protrusion W comprises at least one meridian profile. A meridian profile is defined as the profile obtained from the intersection of the external surface with a meridian plane, i.e. a plane that contains the axis Y of the crown closure (the axis Y being the geometric axis of the metal shell 21, in particular the axis passing through the centre of the upper wall 22 and being substantially orthogonal thereto). Each protrusion W comprises one or more meridian profiles each of which has an upper portion 30 with a first tilt and a lower portion 31 with a second tilt different from the first tilt (in particular, as in the embodiments illustrated in Figures 11-18, the second tilt is greater than the first tilt, taking as a reference the axis Y of the crown closure T). The first tilt and the second tilt are such that each meridian profile of the external surface of each protrusion W is convex towards the exterior. For each meridian profile, the upper portion 30 and the lower portion 31 are joined together by an outer comer V (convex towards the exterior), which may be, in particular, a rounded corner.

[0087] In particular, considering various meridian profiles of each protrusion W, it is possible, as in the embodiments illustrated in Figures 11-18, for each protrusion W to comprise an upper surface 30’, defined geometrically by the joint of the upper portions 30 of the various meridian profiles of the protrusion W, and a lower surface 31’, defined geometrically by the joint of the lower portions 31 of the various meridian profiles of the protrusion W. The upper surface 30’ has, in particular, the first tilt. The lower surface 31’ has, in particular, the second tilt. The upper surface 30’ and the lower surface 31’ are joined together by an external edge zone, which may be rounded, formed by the joint of the various external joining edges of the respective upper and lower portions 30 and 31.

[0088] The crown closure T thus comprises a plurality of upper surfaces 30’ (one for each protrusion W) and a corresponding plurality of lower surfaces 31’ (one for each protrusion W), in which each upper surface 30’ and the respective lower surface 31’ have tilts that are different from one another and are such as to form an external edge zone (convex towards the outside). The aforesaid upper surfaces 30’ (with a lesser tilt with respect to the lower surfaces 31’ of the various protrusions W) are formed during moulding owing to the aforesaid presence of the movable sectors 8 arranged alternating with the teeth 7.

[0089] The upper portion 30 of each meridian profile of each protrusion W is joined to the cylindrical or pseudo-cylindrical portion of the crown closure T by an internal connection 32 (concave towards the outside, in particular, a connection with a rounded surface). Further, the upper surface 30’ of each protrusion W is joined to the cylindrical or pseudo-cylindrical portion of the smooth skirt wall 23 by an internal connecting zone, which may be rounded, formed by the joint of the various internal connections 32.

[0090] It is possible for the geometric and dimensional features of the crown closures disclosed above with reference to Figures 7-10 to be also applied to the crown closures disclosed with reference to Figures 11-18, and vice versa.

[0091] It has been established that it is possible to gain some advantages owing to the shape of the protrusions W (in particular owing to the upper surface 30’ consisting of the joint of the various upper portions 30 and obtained by virtue of the special die 2). It is in particular possible to ensure greater resistance of the engagement of the corrugated skirt wall 25 with the undercut on the neck of the container, increasing the retaining capacity of the wall folded on the neck of the container. Further, the shape of the protrusions W enables the operation of capping to be promoted, i.e. when the crown cap is engaged on the neck of the container by folding the corrugated skirt wall 25.