Mould and method for making a cap

Abstract

A mould (1) for making a cap by compressing a dose in a forming cavity comprises a lower half mould (12) and an upper half mould (11), both made of steel and movable relative to each other along a longitudinal axis 5 (X) between an open position and a closed position, where they delimit the forming cavity. The upper half mould (11) includes a die (111) elongated along a longitudinal axis (X) between a first end (111') and a second end (111'') and including an inner die (111A) and an outer die (111B). The die (111) has a lower zone located at the first end (111') and defining a 10 moulding surface which is operatively in contact with the plastic when the mould (1) is at the closed position; the mould (1) comprises a cooling system, having a ducting system in which a cooling fluid circulates and which is located partly inside the die (111), and one or more copper elements (132) positioned in the lower zone of the die (111) and 15 embedded in the inner die (111A) and / or in the outer die (111B).

Description

[0001] DESCRIPTION

[0002] MOULD AND METHOD FOR MAKING A CAP

[0003] Technical field

[0004] This invention relates to a mould for making a cap. This invention also relates to a method for making a cap.

[0005] Background art

[0006] Known in the prior art are moulds for making plastic items and which comprise a cooling system for cooling the mould.

[0007] Patent document WO2022101778A1 , in the name of the present Applicant, describes a mould for making parisons and comprising a ducting system through which a cooling fluid flows. The ducting system is located in the proximity of the parison moulding cavity so that the fluid laps the parts of the mould which are directly in contact with the molten plastic, thus carrying the heat away with it. Patent document W02007028702A1 , in the name of the present Applicant, also describes a mould for making caps and comprising a ducting system through which the cooling fluid flows.

[0008] Patent document US6425752B1 describes a mould for making plastic items, where the mould die is covered by a sort of hood made of a material having high thermal conductivity, such as copper, for example. In particular, when the die is inserted into the moulding cavity, the copper hood is in direct contact with the cavity.

[0009] Patent document US6354361 describes a mould for making plastic items and comprising an insert made of a material having high thermal conductivity, embedded inside the mould. The mould has channels for the passage of the fluid.

[0010] Also patent documents US2019 / 291311A1 , CN206217027U and CN107244021 A describe a mould for making parisons; however, neither those solutions are able to satisfy the market’s needs.

[0011] With regard to moulds used for making caps, the die (or upper half mould) generally comprises an inner die and an outer die which surrounds and is coaxial with the inner die.

[0012] However, the moulds currently available are not suitable for effectively cooling moulds which are dedicated to the production of caps or, as in the case of document W02007028702A1 , they are highly complex. In particular, in the field of moulds for caps, the mould must be able to cool effectively considering the specific shape of each part of it. Thus, there remains the need to improve the system for cooling the moulds used for the production of caps.

[0013] Disclosure of the invention

[0014] The aim of this disclosure is to provide a mould and a method for making a cap to overcome the above mentioned disadvantages of the prior art.

[0015] In particular, the aim of this invention is to provide a mould and a method for making a cap and which are capable of effectively cooling the parts of the mould itself.

[0016] Another aim of this invention is to propose a mould for making a cap and which is at once constructionally simple and robust.

[0017] These aims are fully achieved by the mould and the method of this disclosure for making a cap for a container as characterized in the appended claims.

[0018] In particular, the mould for making a cap by compressing a dose in a forming cavity comprises a lower half mould and an upper half mould.

[0019] The cap comprises a side wall extending between a first and a second end, and a transverse wall connected to the first end and to the second end of the cap. The side wall extends between the first and the second end around an axis of extension, while the transverse wall extends transversely to the axis of extension. The cap is configured to be coupled to a container. The side wall has an internal portion, in contact with the neck of the container and may be provided with thread to be coupled to a corresponding thread made on the neck of the container. The side wall has an external portion, opposite the internal portion. The transverse wall has an internal portion, directed towards the container when the cap is coupled to the container, and an external portion, opposite the internal portion.

[0020] The forming cavity has a plurality of portions configured for forming the cap. In particular, the forming cavity has a transverse portion, configured to form the transverse wall of the cap, and a side portion, configured to form the side wall of the cap.

[0021] The lower half mould includes a side body and a mould base. In particular, the side body is configured to form the external portion of the side wall of the cap. The mould base is configured to form the external portion of the transverse wall of the cap.

[0022] The mould comprises an upper half mould. The upper half mould includes a die which is elongated along a longitudinal axis between a first end and a second end. When the cap is being formed, the longitudinal axis of the mould and the axis of extension of the cap are parallel or, more particularly, they coincide. The die includes an inner die and an outer die which surrounds the inner die. In other words, the inner die is coaxial with the outer die.

[0023] During moulding, the outer die is configured to form the internal portion of the side wall of the cap; the inner die is configured to form the internal portion of the transverse wall of the cap.

[0024] Preferably, the lower half mould and the upper half mould are made of steel or, more generally speaking, of a first material.

[0025] The lower half mould and the upper half mould are movable relative to each other along the longitudinal axis between an open position, to receive the dose, and a closed position of the mould, where they delimit the forming cavity and compress the dose to force it to occupy the forming cavity. In particular, the die has a lower zone, located at the first end. The lower zone defines a moulding surface which is operatively in contact with the plastic when the mould is at the closed position.

[0026] The mould comprises a cooling system. The cooling system is configured to cool the lower half mould and / or the upper half mould.

[0027] The cooling system includes a ducting system. The ducting system has cooling fluid circulating in it.

[0028] The cooling system includes a cooling structure. The cooling structure is made of copper. The cooling structure is embedded in the steel. In other words, the cooling structure is completely surrounded by the steel. In particular, the cooling structure cooperates with the ducting system to remove heat from the steel.

[0029] In particular, the ducting system includes a first path, located in the die. In particular, the cooling structure includes one or more copper elements positioned in the lower zone of the die, embedded in the inner die and / or in the outer die.

[0030] The copper elements are therefore embedded in the zone which is proximal to the moulding cavity of the die, so as to remove heat from the die, thus cooling it.

[0031] More generally speaking, the cooling structure may be made of a second material, different from the first material.

[0032] Preferably, the first material is a material which has particularly high mechanical strength properties, while the second material is a material which has particularly high thermal conductivity (heat transmission) properties. Compared to the first material, the second material may have lower mechanical strength properties than the first material.

[0033] The fact that the copper elements are completely surrounded by the steel, being stronger than copper, makes the mould robust and at the same time capable of effectively cooling the heat, thanks to the copper inserts themselves.

[0034] In an embodiment, the upper half mould comprises a gap between the outer die and the inner die. The upper half mould may comprise a duct for the passage of air, located in the gap and having an air outlet at the first end of the die. In other words, the duct defines an air passage having an air outlet located at the first end of the die.

[0035] In particular, the air outlet is located at the moulding surface of the die.

[0036] At the open position of the mould (when the upper half mould and the lower half mould are spaced apart), the formed cap may stick to the die; in this case, the air passage allows the cap to come away from the die.

[0037] In an example, the first path is located at least partly in the gap between the inner die and the outer die. That means the gap between the inner die and the outer die can be used not only to detach the cap but also to cool the mould.

[0038] Alternatively or in addition, the first path may be located at least partly in the inner die and / or in the outer die.

[0039] Preferably, the first path is located at least partly inside the outer die. In particular, one or more of the copper elements are embedded in the outer die.

[0040] Thus, in the preferred embodiment, the cooling system comprises a first path which is located partly in the outer die and partly in the gap between the inner die and the outer die.

[0041] Generally speaking, the one or more copper elements positioned in the lower zone of the die may extend longitudinally.

[0042] In an embodiment, the outer die has a first portion having a first diameter and a second portion having a second diameter, larger than the first. The outer die has an intermediate portion which is tapered away from the longitudinal axis. The intermediate portion is located between the first portion and the second portion. The intermediate portion is configured to connect the first portion to the second portion (and vice versa).

[0043] Thus, the outer die has an annular shape having a first diameter and a second diameter, in proximity to the first end of the die. Between the first diameter and the second diameter, the outer die has a connecting portion (the intermediate portion).

[0044] Preferably, the one or more copper elements extend longitudinally at the first portion, at the intermediate portion and at the second portion of the outer die.

[0045] In an example, inside the outer die, the first path defines an annular path running along a perimeter of the first, small-diameter portion.

[0046] Preferably, the one or more copper elements (in the die, that is, in the inner die and / or in the outer die) are angularly equispaced from each other around the longitudinal axis. The copper elements positioned around the longitudinal axis may be elongated longitudinally.

[0047] In an embodiment, the one or more copper elements are embedded in the inner die, preferably in proximity to a surface of the inner die operatively in contact with the plastic when the mould is at the closed position.

[0048] In addition or alternatively, the cooling structure comprises one or more copper elements positioned in the lower half mould.

[0049] The forming cavity includes a side portion extending around the longitudinal axis and configured to form a side wall of the cap; the side body is configured to define the side portion of the forming cavity when the mould is at the closed position. The cooling structure may include one or more copper elements, in particular, a plurality of copper elements located in the side body. The copper elements may be elongated longitudinally inside the side body, angularly equispaced from each other around the longitudinal axis. Thus, the copper elements are located in proximity to a portion of the side body operatively in contact with the plastic when the mould is at the closed position.

[0050] The forming cavity includes a transverse portion extending transversely to the longitudinal axis and configured to form a transverse wall of the cap; the mould base is configured to define the transverse portion of the forming cavity when the mould is at the closed position.

[0051] The cooling structure may include one or more copper elements, preferably, a plurality of copper elements, elongated transversely inside the transverse portion and angularly equispaced from each other around the longitudinal axis. Thus, the copper elements are located in proximity to a portion of the side body operatively in contact with the plastic when the mould is at the closed position.

[0052] This disclosure also provides an apparatus for moulding caps by compression, comprising a plurality of moulds according to one or more of the features described in this disclosure.

[0053] The apparatus may comprise a carousel which rotates about an axis of rotation parallel to the longitudinal axis, where the moulds of the plurality of moulds are disposed along a periphery of the carousel and are configured to rotate as one with the carousel about the axis of rotation. Alternatively, the apparatus may comprise an array of lower half moulds and an array of upper half moulds, so as to make a plurality of caps simultaneously by compression moulding.

[0054] This disclosure also provides a method for making a cap by compressing a dose in a forming cavity.

[0055] The method for making the cap comprises a step of providing a lower half mould, including a side body and a mould base, and an upper half mould, including a die which is elongated along a longitudinal axis between a first end and a second end. Generally speaking, the lower half mould and the upper half mould may be made according to one or more of the features described in this disclosure.

[0056] In particular, the die includes an inner die and an outer die which surrounds the inner die. The upper half mould and the lower half mould are made of steel.

[0057] The method comprises a step of moving the upper half mould and the lower half mould apart along the longitudinal axis to an open position of the mould in order to receive the dose.

[0058] The method comprises a step of moving the upper half mould and the lower half mould towards each other along the longitudinal axis to a closed position of the mould in order to delimit the forming cavity to compress the dose so as to force it to occupy the forming cavity.

[0059] The method comprises a step of forming the cap by means of the upper half mould and the lower half mould when the mould is at the closed position; the die has a lower zone located at the first end and defining a moulding surface which is operatively in contact with the plastic when the mould is at the closed position.

[0060] The method comprises a step of providing a cooling system, comprising a ducting system in which a cooling fluid circulates, and a cooling structure, made of copper, embedded in the steel and cooperating with the ducting system to remove heat from the steel.

[0061] In particular, the method comprises a step of cooling the die via a cooling fluid circulating in a first path of the ducting system located at least partly inside the die, and via one or more copper elements of the cooling structure which are positioned in the lower zone of the die, embedded in the inner die and / or in the outer die.

[0062] In an embodiment, the upper half mould comprises a gap, defined between the outer die and the inner die, and a duct for the passage of air, located in the gap and having an air outlet at the first end of the outer die. In particular, the first path of the ducting system is located in the gap between the inner die and the outer die. The method may comprise a step of blowing a jet of air via the duct located in the gap, in order to detach the formed cap from the die.

[0063] In an embodiment, the outer die has a first portion having a first diameter, a second portion having a second diameter, larger than the first, and an intermediate portion which is tapered away from the longitudinal axis and configured to connect the first portion to the second portion; the one or more copper elements extend longitudinally at the first portion, at the intermediate portion and at the second portion of the outer die. Preferably, inside the outer die, the first path defines an annular path running along a perimeter of the first, small-diameter portion.

[0064] Thus, in the step of cooling, the heat is carried by the copper elements from the second portion to the intermediate portion and to the first portion, and from there is carried by the annular path.

[0065] Preferably, the cooling structure includes a plurality of copper elements elongated longitudinally and angularly equispaced from each other around the longitudinal axis.

[0066] Preferably, the cooling structure comprises one or more copper elements disposed inside the inner die at a portion which is operatively in contact with the plastic when the mould is at the closed position. Thus, the step of cooling is also carried by one or more of the copper elements of the cooling structure, positioned in the inner die.

[0067] In an embodiment, the side portion extends around the longitudinal axis and is configured to form a side wall of the cap; the side body is configured to define the side portion of the forming cavity when the mould is at the closed position; the step of cooling may also be carried out by a plurality of copper elements elongated longitudinally in the side body and angularly equispaced from each other around the longitudinal axis.

[0068] In an embodiment, the transverse portion extends transversely to the longitudinal axis and is configured to form a transverse wall of the cap; the mould base is configured to define the transverse portion of the forming cavity when the mould is at the closed position; the step of cooling may also be carried out by a plurality of copper elements elongated transversely in the mould base and angularly equispaced from each other around the longitudinal axis.

[0069] Brief description of drawings

[0070] These and other features will become more apparent from the following description of a preferred embodiment, illustrated by way of non-limiting example in the accompanying drawings, in which:

[0071] - Figures 1A and 1 B illustrate a mould according to one or more of the features described in this disclosure;

[0072] - Figures 2A-2D illustrate an outer die of a mould according to one or more of the features described in this disclosure;

[0073] - Figures 3A-3C illustrate an inner die of a mould according to one or more of the features described in this disclosure;

[0074] - Figures 4A-4C illustrate a mould base according to one or more of the features described in this disclosure;

[0075] - Figures 5A-5C illustrate a side body according to one or more of the features described in this disclosure.

[0076] Detailed description of preferred embodiments of the invention

[0077] The numeral 1 in the drawings denotes a mould for making a cap by compressing a dose in a forming cavity, where the cap comprises a side wall extending around an axis of extension between a first end and a second end, and a transverse wall, connected to one between the first end and the second end of the side wall and extending transversely to the axis of extension. The side wall of the cap has an internal portion, directed towards the container when the cap is coupled to the container, and an external portion, opposite the internal portion. The transverse wall of the cap has an internal portion, directed towards the container when the cap is coupled to the container, and an external portion, opposite the internal portion.

[0078] The mould 1 defines a forming cavity in which the cap is formed by compression.

[0079] The mould 1 comprises an upper half mould 11 and a lower half mould 12, aligned along a longitudinal axis X. The upper half mould 11 and the lower half mould 12 are made of steel. The upper half mould 11 and the lower half mould 12 are movable relative to each other along the longitudinal axis X between an open position of the mould 1 , where they are spaced apart to receive a dose of plastic material, and a closed position of the mould 1 , where they delimit the forming cavity and cooperate to compress the dose so as to form the cap inside it.

[0080] The lower half mould 12 comprises a side body 121 and a mould base 122. The side body 121 extends around the longitudinal axis X and is configured to form the external portion of the side wall of the cap; in other words, the side body 121 is configured to delimit the forming cavity at the external portion of the side wall of the cap. The mould base 122 extends transversely (perpendicularly) to the longitudinal axis X and is configured to form the external portion of the transverse wall of the cap; in other words, the mould base 122 is configured to delimit the forming cavity at the external portion of the transverse wall of the cap. The side body 121 and the mould base 122 may be movable relative to each other along the longitudinal axis X.

[0081] The upper half mould 11 includes a die 111 elongated along a longitudinal axis X between a first end 11 T and a second end 111".

[0082] The die 111 includes an inner die 111 A and an outer die 111 B. The outer die 111 B surrounds the inner die 111 A. Preferably, the inner die 111 A and the outer die 111 B are movable relative to each other along the longitudinal axis X.

[0083] Between the outer die 111 B and the inner die 111 A there is a gap, comprising a duct for the passage of air. The duct has an air outlet at the first end 11 T of the die 111 .

[0084] The inner die 111A is configured to form the internal portion of the transverse wall of the cap; in other words, the inner die 111 A is configured to delimit the forming cavity at the external portion of the transverse wall of the cap.

[0085] The outer die 111 B is configured to form the internal portion of the side wall of the cap; in other words, the outer die 111 B is configured to delimit the forming cavity at the internal portion of the transverse wall of the cap. The die 111 has a lower zone located at the first end 11 T and defining a moulding surface which is operatively in contact with the plastic when the mould 1 is at the closed position. The side body 121 and the mould base 122 define a moulding surface which is operatively in contact with the plastic. Thus, the moulding surface is defined by the die 11 1 , by the side body 121 and by the mould base 122 which act in conjunction to delimit the forming cavity.

[0086] The mould 1 comprises a cooling system, configured to cool the mould 1 and more particularly, the portions of the mould 1 in proximity to the moulding surface.

[0087] The outer die 111 B has an annular shape around the longitudinal axis X and has a first portion 111 B' having a first diameter, a second portion 111 B" having a second diameter, larger than the first diameter of the first portion 111 B', and an intermediate portion 111 B'" which is tapered away from the longitudinal axis X and located between the first portion 111 B' and the second portion 111 B" to connect the first portion 111 B' and the second portion 111 B". In particular, the second portion 111 B" is configured to define the moulding surface which is operatively in contact with the plastic when the mould 1 is at the closed position.

[0088] The cooling system comprises a ducting system including a first path 131 located in the outer die 111 B. A cooling fluid circulates inside the first path to cool the outer die 111 B. The first path 131 inside the outer die 111 B defines an annular path located inside the first portion 111 B' of the outer die 111 B.

[0089] The cooling system also comprises a cooling structure which includes one or more copper elements 132, embedded in the steel. A group of copper elements 132 is embedded in the outer die 111 B, near the zone proximal to the moulding cavity, in particular at the first portion 111 B', at the intermediate portion 111 B'” and at the second portion 111 B" of the outer die 111 B. In particular, the copper elements 132 extend longitudinally and are angularly equispaced from each other around the longitudinal axis X. In particular, inside the outer die 111 B, the copper elements 132 extend from a lower end of the outer die 111 B proximal to the moulding cavity, into the first portion 111 B', into the intermediate portion 111 B'" and as far as the second portion 111 B" in proximity to the first annular path 131 formed in the outer die 111 B.

[0090] In an example, the inner die 111 A comprises a group of copper elements 132. The copper elements 132 of the inner die 111 A are embedded in the inner die 111A and have a longitudinally extending portion and a transversely extending portion which are connected to each other. The transversely extending portion is proximal to the moulding surface of the inner die 111 A which delimits the internal portion of the transverse surface of the cap. The copper elements 132 of the inner die 111 A are equispaced from each other around the longitudinal axis X.

[0091] The side body 121 comprises a group of copper elements 132. embedded in the side body 121 and extending longitudinally. The copper elements 132 of the side body 121 are located in proximity to the portion of the side body 121 operatively in contact with the plastic when the mould 1 is at the closed position. The copper elements 132 of the side body 121 are equispaced from each other around the longitudinal axis.

[0092] The mould base 122 comprises a group of copper elements 132, embedded in the mould base 122 and extending transversely to the longitudinal axis X. The copper elements 132 of the mould base 122 are located in proximity to the portion of the mould base 122 operatively in contact with the plastic when the mould 1 is at the closed position. The copper elements 132 of the mould base 122 are equispaced from each other around the longitudinal axis.

Claims

CLAIMS1. A mould (1) for making a cap by compressing a dose in a forming cavity, comprising:- a lower half mould (12), including a side body (121) and a mould base (122);- an upper half mould (11) including a die (111) elongated along a longitudinal axis (X) between a first end (111') and a second end (111"), the die (111) including an inner die (111 A) and an outer die (111 B) surrounding the inner die (111 A), wherein the lower half mould (12) and the upper half mould (11) are made of steel and are movable relative to each other along the longitudinal axis (X) between an open position of the mould (1), to receive the dose, and a closed position of the mould (1), where they delimit the forming cavity and compress the dose to force it to occupy the forming cavity, the die (111) having a lower zone located at the first end (111') and defining a moulding surface which is operatively in contact with the plastic when the mould (1) is at the closed position;- a cooling system, comprising: a ducting system having a cooling fluid circulating in it, and a cooling structure, made of copper, embedded in the steel and cooperating with the ducting system to remove heat from the steel, the mould (1) being characterized in that the ducting system includes a first path (131), located in the die (111), and the cooling structure includes one or more copper elements (132) positioned in the lower zone of the die (111) and embedded in the inner die (111 A) and / or in the outer die (111 B).

2. The mould (1) according to claim 1, wherein the upper half mould (11) comprises:- a gap, defined between the outer die (111 B) and the inner die (111 A), and- a duct for the passage of air, located in the gap and having an air outlet at the first end (11 T) of the die (111).

3. The mould (1 ) according to claim 2, wherein the first path (132) is located at least partly in the gap between the inner die (111 A) and the outer die (111 B).

4. The mould (1 ) according to any one of the preceding claims, wherein the first path (131 ) is located at least partly inside the outer die (111 B) to make the cooling fluid circulate in the outer die (111 B), and wherein one or more of the copper elements (132) are embedded in the outer die (111 B).

5. The mould (1 ) according to claim 4, wherein the outer die (111 B) has a first portion (111 B’) having a first diameter, a second portion (111 B") having a second diameter, larger than the first, and an intermediate portion (111 B'") which is tapered away from the longitudinal axis (X) and configured to connect the first portion (111 B’) to the second portion (111 B"), the one or more copper elements extending longitudinally at the first portion (111 B'), at the intermediate portion (111 B'") and at the second portion (111 B") of the outer die (111 B).

6. The mould (1 ) according to claim 5, wherein, inside the outer die (111 B), the first path (131 ) defines an annular path running along a perimeter of the first, small-diameter portion (111 B').

7. The mould (1 ) according to any one of the preceding claims, wherein the cooling structure includes a plurality of copper elements (132) elongated longitudinally and angularly equispaced from each other around the longitudinal axis (X).

8. The mould (1 ) according to any one of the preceding claims, wherein one or more of the copper elements (132) are embedded in the inner die (111 A), in proximity to a surface of the inner die (111 A) which is operatively in contact with the plastic when the mould (1 ) is at the closed position.

9. The mould (1 ) according to any one of the preceding claims, wherein the cooling structure comprises one or more copper elements (132) positioned in the lower half mould (12).

10. The mould (1 ) according to claim 9, wherein:- the forming cavity includes a side portion extending around the longitudinal axis (X) and configured to form a side wall of the cap, the side body (121 ) being configured to define the side portion of the forming cavity when the mould (1 ) is at the closed position;- the cooling structure includes a plurality of copper elements (132) elongated longitudinally inside the side body (121 ) and angularly equispaced from each other around the longitudinal axis (X).

11. The mould (1 ) according to claim 9 or 10, wherein:- the forming cavity includes a transverse portion extending transversely to the longitudinal axis (X) and configured to form a transverse wall of the cap, the mould base (122) being configured to define the transverse portion of the forming cavity when the mould (1 ) is at the closed position;- the cooling structure includes a plurality of copper elements (132) elongated transversely inside the transverse portion and angularly equispaced from each other around the longitudinal axis (X).

12. An apparatus for moulding caps by compression, comprising:- a plurality of moulds (1 ) according to any one of claims 1 to 11 ;- a carousel which rotates about an axis of rotation parallel to the longitudinal axis (X), where the moulds (1 ) of the plurality of moulds (1 ) are disposed along a periphery of the carousel and are configured to rotate as one with the carousel about the axis of rotation.

13. A method for making a cap by compressing a dose in a forming cavity, comprising the following steps:- providing a lower half mould (12), including a side body (121 ) and a mould base (122);- providing an upper half mould (11 ) including a die (111 ) elongated along a longitudinal axis (X) between a first end (11 T) and a second end (111 "), the die (111 ) including an inner die (111 A) and an outer die (111 B) surrounding the inner die (111 A), the upper half mould (11 ) and the lower half mould (12) being made of steel;- moving the upper half mould (11 ) and the lower half mould (12) apartalong the longitudinal axis (X) to an open position of the mould (1 ) in order to receive the dose;- moving the upper half mould (11 ) and the lower half mould (12) towards each other along the longitudinal axis (X) to a closed position of the mould (1 ) in order to delimit the forming cavity to compress the dose so as to force it to occupy the forming cavity;- forming the cap by means of the upper half mould (11 ) and the lower half mould (12) when the mould is at the closed position, the die (111 ) having a lower zone located at the first end (111 ') and defining a moulding surface which is operatively in contact with the plastic when the mould (1 ) is at the closed position;- providing a cooling system, comprising: a ducting system having a cooling fluid circulating in it, and a cooling structure, made of copper, embedded in the steel and cooperating with the ducting system to remove heat from the steel; the method being characterized in that it comprises a step of cooling the die (111 ) via a cooling fluid, circulating in a first path (31 ) of the ducting system located at least partly in the die (111 ), and one or more copper elements (132) of the cooling structure, positioned in the lower zone of the die (111 ), embedded in the inner die (111 A) and / or in the outer die (111 B).

14. The method according to claim 13, wherein the upper half mould (11 ) comprises:- a gap, defined between the outer die (111 B) and the inner die (111 A), and- a duct for the passage of air, located in the gap and having an air outlet at the first end (11 T) of the die (111 ), wherein the first path (131 ) of the ducting system is located in the gap between the inner die (111 A) and the outer die (111 B).

15. The method according to claim 13 or 14, wherein:- the outer die (111 B) has a first portion (111 B') having a first diameter, a second portion (111 B") having a second diameter, larger than the first, and an intermediate portion (111 B'") which is tapered away from the longitudinal axis (X) and configured to connect the first portion (111 B’) to the second portion (111 B");- each copper element (132) extends longitudinally at the first portion (111 B'), at the intermediate portion (111 B'") and at the second portion (111 B") of the outer die (111 B), and- inside the outer die (111 B), the first path (131 ) defines an annular path running along a perimeter of the first, small-diameter portion (111 B').

16. The method according to any one of claims 13 to 15, wherein the cooling structure includes a plurality of copper elements (132) elongated longitudinally and angularly equispaced from each other around the longitudinal axis (X).

17. The method according to any of claims 13 to 16, wherein one or more of the copper elements (132) are embedded in the inner die (111 A), in proximity to a surface of the inner die (111 A) which is operatively in contact with the plastic when the mould (1 ) is at the closed position.

18. The method according to any one of claims 13 to 17, wherein the forming cavity includes:- a side portion extending around the longitudinal axis (X) and configured to form a side wall of the cap, the side body (121 ) being configured to define the side portion of the forming cavity when the mould (1 ) is at the closed position;- a transverse portion extending transversely to the longitudinal axis (X) and configured to form a transverse wall of the cap, the mould base (122) being configured to define the transverse portion of the forming cavity when the mould (1 ) is at the closed position, and wherein the step of cooling is carried out also by:- a plurality of copper elements (132) elongated longitudinally inside the side body (121 ) and angularly equispaced from each other around thelongitudinal axis (X);- a plurality of copper elements (132) elongated transversely inside the mould base (122) and angularly equispaced from each other around the longitudinal axis (X).

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