METHOD FOR PACKAGING A PRODUCT IN A CONTAINER WITH A TRAY AND A TOP FILM

Description

[0001] This invention relates to a method for packaging a product in a container comprising a tray and an upper sheet. In particular, this invention relates to a method for packaging a product in a container comprising a tray and an upper sheet applied to a flange of the tray. Preferably, this invention is intended for packaging any type of food products, for example fruit and vegetables. However, this invention may be applied for packaging even non-food products.

[0002] This invention may advantageously be applied relative to a type of tray which comprises a bottom wall, a plurality of lateral walls and a flange, which is connected to the top of the lateral walls and which, when it is coupled to the upper sheet, is configured to remain in a final configuration (as shown in Figures 5 to 8), in which it is folded relative to the lateral walls, but which is in an initial configuration (as shown in Figures 1 to 4), in which it extends upwards from the lateral walls away from the bottom wall, when the tray is made.

[0003] For that purpose, in some prior art embodiments of the tray, there are at least one projecting element, which is part of the flange and which projects from an inner edge of the flange itself, and at least one stop, at least partly fixed to one of the lateral walls of the tray and suitable for interacting with the projecting element. When the flange is in the initial configuration, inside the tray the stop is at least partly superposed on the projecting element. The stop has a movable upper portion (not fixed to the lateral wall), which is movable relative to the lateral wall and which is configured to bend inwards towards the inside of the tray, and a fixed lower portion, which in contrast is fixed to the lateral wall. During folding of the flange, the projecting element folds together with the flange relative to the lateral wall, bending the movable upper portion of the stop inwards towards the inside of the tray. At a predetermined point, the projecting element goes beyond the movable upper portion of the stop, and the latter can elastically snap into place and substantially return to its initial position. At that point the projecting element abuts against the top of the movable upper portion of the stop which prevents the projecting element and the flange as a whole from returning to the initial configuration, thereby holding the flange in the final configuration.

[0004] In general, the flange is constituted of a plurality of portions which are separate from each other, in particular it may comprise a different portion for each of the lateral walls (each portion being equipped with respective projecting elements).

[0005] In the context of this invention, in which the method may be at least partly implemented using a closing machine, the term closing machine refers to a machine suitable for applying, and preferably for heat-sealing, an upper sheet, usually a protective upper sheet, to a tray, preferably of the type described above, thereby obtaining a container. In general, positioned in the container there is a food product, which is placed between the tray and the upper sheet and which is at least partly isolated from the outside environment. In general, according to the prior art, a closing machine comprises a supporting element, which defines a housing for the tray. In the case of trays which are tub-shaped and equipped with a bottom wall, a plurality of lateral walls and a flange, the supporting element may comprise a central body configured to support the bottom wall (and in some cases the lateral walls). Usually, the supporting element defines a closing frame which is configured to make contact with the flange during closing, in particular supporting it from below.

[0006] Moreover, prior art closing machines comprise a closing element which is movable relative to the supporting element between a home position and a closed position. In particular, when the closing element is in the closed position, the closing element clamps the flange of the container and the upper sheet between itself and the closing frame (which is substantially a contact element for the closing element). Usually, connected to the closing element there are heating means which are operatively connected to the closing element in order to heat it, thereby allowing sealing or gluing of the upper sheet to the tray.

[0007] According to the prior art currently used, application of the upper sheet to trays of the type for which this invention is intended, occurs using closing machines of the standard type, that is to say, closing machines configured to close trays which are already fully formed, in which the flange is folded into its final position.

[0008] In accordance with the prior art, the tray is therefore formed in a step preceding its positioning in the closing machine according to this invention. Consequently, after tray forming and before its use, the flange must be folded outwards from the tray (defined by the bottom wall and the lateral walls), in particular in such a way as to make the projecting elements of the flange snap into place beyond the stops provided in the lateral walls.

[0009] In some cases the folding is performed by a folding machine. In contrast, in other cases the folding is performed manually by an operator. In any case, in both solutions, the folding is performed in a step preceding insertion of the tray into the closing machine, separately from closing of the tray to make the container.

[0010] Prior art examples of known packaging methods are disclosed by patent documents EP3782804A1, EP3466654B1 and EP2374730A1.

[0011] However, this prior art technology has several disadvantages.

[0012] First, the process of making the container requires relatively long times for carrying it out. In particular, the preliminary folding step involves a considerable increase in the time necessary to obtain the container.

[0013] Second, at least for large production runs it is necessary to have available an additional folding machine. That translates into a substantial space which is occupied by the machines inside the plant, as well as higher installation costs. In this context, the technical purpose which forms the basis of this invention is to provide a method for packaging a product in a container comprising a tray and an upper sheet, which overcomes the above-mentioned disadvantages.

[0014] In particular, the technical purpose of this invention is to provide a method for packaging a product in a container comprising a tray and an upper sheet, which allows a reduction in production times for making a container compared with the prior art.

[0015] A further technical purpose of this invention is to provide a method for packaging a product in a container comprising a tray and an upper sheet, which does not require the use of specific folding machines and which simplifies the production process compared with the prior art.

[0016] The technical purpose specified and the aims indicated are substantially achieved by a method for packaging a product in a container comprising a tray and an upper sheet, as described in the independent claim. Particular embodiments of this invention are defined in the corresponding dependent claims.

[0017] Further features and the advantages of this invention will be more apparent from the detailed description of several preferred, non-limiting embodiments of a method for packaging a product in a container comprising a tray and an upper sheet, and of a closing machine usable in the method, which are illustrated in the accompanying drawings, in which: Figure 1 is an axonometric view of a tray of the type to which this invention relates, with a flange in an initial configuration; Figure 2 is a top view of the tray of Figure 1; Figure 3 is a side view of the tray of Figure 1; Figure 4 is a cross-section of the tray of Figure 2 sectioned according to the section line IV - IV; Figure 5 is an axonometric view of the tray of Figure 1 with the flange in a final configuration and with an upper sheet applied to the flange; Figure 6 is a top view of the tray of Figure 5; Figure 7 is a side view of the tray of Figure 5; Figure 8 is a cross-section of the tray of Figure 6 sectioned according to the section line VIII - VIII; Figure 9 is an exploded schematic axonometric view of an embodiment of a closing machine usable in the method according to this invention, with some elements removed to better highlight others; Figure 10 is an axonometric view of a second member of a closing element which is part of the closing machine of Figure 9; Figure 11 is a top view of the second member of Figure 10; Figure 12 is a cross-section of the second member of Figure 11 sectioned according to the section line XII - XII; Figure 13 is a cross-section of the second member of Figure 11 sectioned according to the section line XIII - XIII; Figure 14 is an axonometric view of a first member of the closing element which is part of the closing machine of Figure 9; Figure 15 is a top view of the first member of Figure 14; Figure 16 is a cross-section of the first member of Figure 15 sectioned according to the section line XVI - XVI; Figure 17 is a cross-section of the first member of Figure 15 sectioned according to the section line XVII - XVII; Figure 18 is an axonometric view of a supporting element which is part of the closing machine of Figure 9; Figure 19 is a top view of the supporting element of Figure 18; Figure 20 is a vertical section of a closing machine usable in the method according to this invention, which comprises the elements of Figure 9, which is sectioned according to the section line XII - XII of Figures 11, 15 and 19, with the closing element in a home position and during an initial operating step; Figure 21 shows the closing machine of Figure 20 with the closing element in a first contact position; Figure 22 shows the closing machine of Figure 21 with the closing element in a further position during the movement of the closing element towards the supporting element; Figure 23 shows the closing machine of Figure 22 with the closing element in a subsequent intermediate position; Figure 24 shows the closing machine of Figure 23 with the closing element in a subsequent second contact position; Figure 25 shows the closing machine of Figure 24 with the closing element in a closed position and with a cutting element in a retracted position; Figure 26 shows the closing machine of Figure 25 with the closing element in the closed position and with the cutting element in the extracted position; Figures 27 to 32 are enlarged details respectively of Figures 20 to 25; Figure 33 shows the closing machine of Figure 20 with some elements removed to better highlight others; and Figures 34 and 35 show, in views corresponding, respectively, to those of Figures 27 and 30, a variant of the closing machine, in which the first member is configured to completely fold the flange of the tray.

[0018] In the detailed description which follows first there is a description of the closing machine, according to a first aspect of this description, then of the method for packaging a product in a container comprising a tray and an upper sheet, according to this invention and in which the closing machine may be used.

[0019] What is described below with reference, respectively, to the closing machine and to the method, shall be understood to also be applicable, respectively, with reference to the method and with reference to the closing machine, if technically compatible.

[0020] Hereinafter, with reference to the above-mentioned figures, the numeral 1 denotes in its entirety a closing machine, whilst the numeral 2 denotes in its entirety a tray.

[0021] This invention relates in general to the closing with an upper sheet 3 of a tray 2, by applying the upper sheet 3 on the tray 2 at its flange 4. Preferably, application of the upper sheet 3 on the tray 2 is substantially a heat-sealing operation. However, that shall not be understood as limiting for this invention, since other forms of application of the upper sheet 3 are possible, for example gluing of the upper sheet 3 on the tray 2 at the flange 4.

[0022] This invention is applied in the case of a tray 2 which comprises a bottom wall 5, which is usually configured to receive a product and is advantageously flat, a plurality of lateral walls 6, which extend upwards starting from the bottom wall 5, and the flange 4, which is connected to the top of the lateral walls 6 and which is configured to adopt an operating configuration starting from an initial configuration. The bottom wall 5 and the lateral walls 6 delimit an inner space 54 of the tray, intended to receive the product to be packaged.

[0023] In more detail, when the flange 4 is in the initial configuration, it extends upwards from the lateral walls 6 away from the bottom wall 5. Advantageously, the flange 4 substantially defines a continuation of the lateral walls 6 with which it is coplanar: each portion of the flange 4 is inclined in the same way, relative to the bottom wall 5, as the lateral wall 6 to which it is connected. An example of a tray 2 with the flange 4 in the initial configuration is shown in Figures 1 to 4. Advantageously, the initial configuration of the flange 4 is the one adopted by the flange 4 during the making of the tray 2, if there are no steps for folding the flange 4 relative to the lateral walls 6 to which it is connected.

[0024] In contrast, when the flange 4 is in the operating configuration, it is folded relative to the lateral walls 6. Advantageously, to facilitate folding of the flange 4, the tray 2 may have fold lines 7 at the zone in which the flange 4 and the lateral walls 6 are connected to each other, along which the material is weakened thereby facilitating folding of the flange 4. It should be noticed that, in the context of this invention, when the flange is in the operating configuration it is folded, relative to the lateral wall, at least as far as it is folded in a final configuration which it must adopt in the finished container, but preferably more than when it is in the final configuration, as will be clearer from the following description.

[0025] An example of a tray 2 with the flange 4 in the final configuration is shown in Figures 5 to 8, whilst Figure 32 and Figure 35 show the flange 4 in the operating configuration.

[0026] According to this invention the tray 2 also comprises at least one projecting element 8, which is fixed to the flange 4, and at least one stop 9, which is at least partly fixed to one of the lateral walls 6. When the flange 4 is in the initial configuration, the projecting element 8 is inserted into a seat 55 made in the lateral wall 6. The stop 9 is positioned on the lateral wall 6 inside the tray 2 in such a way that, perpendicularly to the lateral wall 6 itself, the projecting element 8 and the stop 9 are at least partly superposed one on the other when the flange 4 is in the initial configuration. In particular, it is possible that the stop 9 is constituted of a portion of a sheet which defines one of the lateral walls 6, or that the stop 9 is a separate element coupled to the lateral wall 6 (for example glued, as in the trays 2 illustrated in Figures 1 to 8). In particular, the stop 9 has a movable upper portion 10 (not fixed to the lateral wall 6), which is movable relative to the lateral wall 6 and which is configured to bend inwards towards the inside of the tray 2, and a fixed lower portion 11, which in contrast is fixed to the lateral wall 6. As shown in the accompanying figures, the projecting element 8 is connected to the flange 4 at an extension of the fold line 7 along which the flange 4 is folded relative to the lateral wall 6, so that, starting from the initial configuration, a rotation outwards by the flange 4 corresponds to a rotation towards the inner space 54 by the projecting element 8.

[0027] During folding of the flange 4 (which causes the flange 4 of the tray 2 to switch from the initial configuration to the operating configuration), the projecting element 8 is folded relative to the lateral walls 6 together with the flange 4 and comes out of the seat 55 bending the movable upper portion 10 of the stop 9 inwards towards inside of tray 2. Before the operating configuration is reached, the projecting element 8 goes beyond the movable upper portion 10 of the stop 9, and the latter can elastically snap into place and substantially return to its initial position. At that point, when the flange 4 again shifts towards the initial configuration, the projecting element 8 abuts against the top of the movable upper portion 10 of the stop 9, which prevents the projecting element 8 and the flange 4 as a whole from returning to the initial configuration, advantageously stopping them in the final configuration. Moreover, the flange 4 in turn comprises a plurality of portions which are separate from each other. Advantageously, the flange 4 comprises a different portion for each of the lateral walls 6. Preferably, each of the portions of the flange 4 is fixed to at least one projecting element 8, advantageously at least to a pair of projecting elements 8.

[0028] Advantageously, the tray 2 comprises at least one layer of paper and cardboard industry material which covers substantially the entire extent of the tray 2. More particularly, the tray 2 is advantageously constituted of a single sheet of paper and cardboard industry material which may comprise one or more layers, and which is folded and glued on itself.

[0029] In other embodiments the tray 2 may in any case even be constituted of different materials. For example, the trays 2 may be constituted of at least one sheet of paper and cardboard industry material coupled to a material suitable for constituting a liner (for example EVOH) or it may be constituted of at least one sheet of paper and cardboard industry material coupled to a lacquer.

[0030] Moreover, even the upper sheet 3 may be any type suitable for the purpose. Preferably, the upper sheet 3 is a plastic film, but in some embodiments the upper sheet 3 is a different type of sheet, for example an aluminium sheet, a bioplastic sheet or a sheet of paper and cardboard industry material.

[0031] The closing machine 1 usable in the context of this invention comprises, similarly to prior art closing machines, a supporting element 12 which is preferably mounted on a supporting frame (not shown in the accompanying figures) whose task is both to provide a supporting structure for the other elements which are part of the closing machine 1, and to give structural stiffness to the entire closing machine 1. The inside of the supporting element 12 defines a housing 13 which is configured to receive, in use, the tray 2 and which has an exiting central axis 14. Preferably, the housing 13 has a bottom surface 15, which is advantageously configured to make contact with the bottom wall 5 of the tray 2 supporting it, and a plurality of lateral surfaces 16. In some embodiments, the lateral surfaces 16 are configured to make contact with the lateral walls 6 of the tray 2 over their entire extent and the supporting element 12 is substantially constituted of a mould shaped like the tray 2 which it must receive (that is to say, that the housing 13 has a shaped inner surface, which substantially traces the outer surface both of the bottom wall 5 and of the lateral walls 6 of the tray 2). In other embodiments, the lateral surfaces 16 are configured to make contact with the lateral walls 6 of the tray 2 only over a small portion of their extent or to not make contact with the lateral walls 6 (solution shown in the accompanying figures). For example, as shown in Figure 20, the lateral surfaces 16 of the housing 13 are perpendicular to the bottom surface 15, whilst the lateral walls 6 of the tray 2 are inclined by approximately 100° relative to the bottom wall 5.

[0032] Preferably, the housing 13 has an insertion opening 17, which is made on the opposite side to the bottom surface 15. The insertion opening 17 allows the tray 2 to be inserted into the housing 13. Moreover, in the preferred embodiments, the supporting element 12 has a closing frame 18 which delimits the top of the housing 13, surrounding the insertion opening 17, and which is advantageously defined by a top surface of the walls of the supporting element 12 which also define the lateral surfaces 16 of the housing 13.

[0033] The exiting central axis 14 is defined as the axis which extends starting from the bottom surface 15, which comes out of the housing 13 through the insertion opening 17, and which is substantially centred relative to the lateral surfaces 16 and relative to the closing frame 18.

[0034] In the preferred embodiments, the closing frame 18 has an operating surface 56 configured to make contact with a lower part of the flange 4 placed in the operating configuration. The operating surface 56 is directed outwards relative to the exiting central axis 14, and (at each side of the housing) relative to the exiting central axis 14 it forms a first angle 100 which is between 90° and 150°, preferably between 100° and 140°, and even more preferably between 110° and 130° (Figures 20 and 21). This embodiment is advantageous since it allows the projecting elements 8 to pass the movable upper portions 10 of the stops 9 during folding of the flange 4. For example, in the embodiment illustrated, the first angle 100 is equal to 116°. It should be noticed that, in the context of this description, the first angle 100 corresponds to the smallest angle of rotation necessary in order to position the operating surface 56 coplanar with the exiting central axis 14 by moving the operating surface 56 according to a direction exiting the operating surface 56 itself. In the accompanying figures the first angle 100 therefore lies in the plane of the drawing and, as illustrated in Figure 33, is measured over the operating surface 56 (with reference to the orientation of the drawing).

[0035] The preferred embodiment of the supporting element 12 is shown in detail in Figure 18; in it the operating surface 56 as a whole lies on the lateral wall of a frustum of a pyramid.

[0036] The closing machine 1 also comprises a closing element 19, which is operatively associated with the supporting element 12, which is advantageously placed over the supporting element 12 itself at the insertion opening 17 and which is also preferably mounted on the supporting frame. The closing element 19 is movable relative to the supporting element 12, parallel to the exiting central axis 14, between a home position and a closed position. Advantageously, the closing element 19 is movable relative to the supporting element 12 parallel to the exiting central axis 14 which is advantageously vertical. It should be emphasised that in the embodiment illustrated, the closing element 19 is movable relative to the supporting element 12 which is fixed and stationary relative to the supporting frame; however, in any case it is possible to have both embodiments in which the closing element 19 is fixed and stationary relative to the supporting frame and the supporting element 12 is movable relative to the closing element 19, and embodiments in which both of the elements 12, 19 are movable relative to each other and relative to the supporting frame. In the preferred embodiments, the closing element 19 is moved between the home position and the closed position by an actuator, which is advantageously linear, and which is not illustrated in the figures. The aspects strictly linked to that actuator or to other elements which are suitable for moving the closing element 19 relative to the supporting element 12, for example their operation, are considered to be known to an expert in the sector and for this reason will not be described in detail.

[0037] When the closing element 19 is in the home position, the closing element 19 and the supporting element 12 are spaced apart and uncoupled from each other, as shown in Figure 20. Advantageously, when the closing element 19 is in the home position, the closing element 19 and the supporting element 12 are spaced apart from each other allowing access to the housing 13 and, therefore, insertion of the tray 2 into the housing 13 and / or removal of the tray 2 from the housing 13.

[0038] In contrast, when the closing element 19 is in the closed position, the closing element 19 and the supporting element 12 are coupled to each other. Advantageously, when the closing element 19 and the supporting element 12 are coupled to each other, the two together define an operating chamber, inside which both the tray 2 which contains the product to be packaged and the upper sheet 3 to be applied to the tray 2 are positioned, and perimetrically they clamp between them the upper sheet 3 and the flange 4 to fix the upper sheet 3 to the flange 4. For that purpose the closing machine 1 also comprises heating means, which are not illustrated, and which are preferably associated with the closing element 19 (although they may also or only be associated with the supporting element 12). The aspects strictly linked to the features of the heating means, for example their operation, are known to a person expert in the sector and for this reason will not be described in further detail.

[0039] According to an innovative aspect of this invention, the closing element 19 is configured in such a way that the movement of the closing element 19 from the home position to the closed position causes, in use, switching of the flange 4 of the tray 2 placed inside the housing 13, from the initial configuration to the operating configuration. In other words, the movement of the closing element 19 from the home position to the closed position implements a folding step for folding the flange 4 relative to the lateral walls 6.

[0040] In more detail, preferably the closing element 19 has a first contact portion 20 and a second contact portion 21, both configured to couple, in use, to the flange 4 of the tray 2 (in use, the upper sheet 3 will always be interposed between the flange 4 and the first contact portion 20 or the second contact portion 21).

[0041] In some embodiments, such as that of Figures 9 to 33, the first contact portion 20 has a first surface 57 directed outwards relative to the exiting central axis 14 of the housing 13, whilst the second contact portion 21 has a second surface 58 directed towards the exiting central axis 14, as is clearly visible in Figures 20 to 26.

[0042] In use, the first surface 57 and the second surface 58 are responsible for folding of the flange 4 from the initial configuration to the operating configuration and are configured in such a way as to act one after the other, splitting the folding into two successive steps.

[0043] During the movement of the closing element 19 from the home position to the closed position, before reaching the closed position, the closing element 19 in fact reaches, one after the other, a first contact position and a second contact position. Moreover, advantageously, during the movement of the closing element 19 from the home position to the closed position, the closing element 19 also reaches an intermediate position which is located between the first contact position and the second contact position.

[0044] In the home position, both the first contact portion 20, and the second contact portion 21, are spaced apart from the flange 4. When the closing element 19 reaches the first contact position, in use, only the first contact portion 20 makes contact with the flange 4 (with the upper sheet 3 interposed between them). In use, in contrast, only when the closing element 19 reaches the second contact position, the second contact portion 21 makes contact with the flange 4 (again with the upper sheet 3 interposed between them). The moment when the closing element 19 is placed in the first contact position is shown in Figures 21 and 28, whilst the moment when the closing element 19 is placed in the second contact position is shown in Figures 24 and 31.

[0045] The first contact portion 20 is configured to perform, in use, during the movement of the closing element 19 from the first contact position to the second contact position, a first folding of the flange 4 outwards to make it adopt an intermediate configuration between the initial configuration and the operating configuration. In contrast, the second contact portion 21 is configured to perform, in use, during the movement of the closing element 19 from the second contact position to the closed position, a second folding of the flange 4 outwards to make it adopt the operating configuration (making the projecting elements 8 snap into place). Advantageously, the first contact portion 20 is configured to perform, in use, the first folding of the flange 4 during the movement from the first contact position to the intermediate position (but this aspect will be described in more detail below).

[0046] Regarding the first contact portion 20, in the preferred embodiments, the first surface 57 forms with the exiting central axis 14 at least one second angle 101, 102 which is between 90° and 150°, preferably between 100° and 130° and even more preferably between 105° and 120°. For example, in the embodiment illustrated in Figures 9 to 33, the first surface 57 comprises a first contact area 22, which forms a second angle 101 equal to 108° and a second contact area 23, which forms a second angle 102 equal to 117°; the first contact area 22 is radially more internal than the second contact area 23. It should be noticed that in the context of this description the second angle 101, 102 corresponds to the smallest angle of rotation necessary in order to position the first surface 57 coplanar with the exiting central axis 14 by moving the first surface 57 according to a direction exiting the first surface 57 itself. In the accompanying figures the second angle 101, 102 therefore lies in the plane of the drawing and is measured under the first surface 57 (with reference to the orientation of the drawing). Figure 33 shows the second angles 101, 102 formed respectively by the first contact area 22 and by the second contact area 23.

[0047] In other embodiments, such as that in Figures 34 and 35, the first contact portion 20 in contrast has the first surface 57 directed towards the exiting central axis 14 of the housing 13, just as the second contact portion 21 has the second surface 58 directed towards the exiting central axis 14.

[0048] In this case, in use, only the first surface 57 is responsible for folding of the flange 4 from the initial configuration to the operating configuration.

[0049] In this case too, during the movement of the closing element 19 from the home position to the closed position, before reaching the closed position, the closing element 19 reaches, one after the other, a first contact position and a second contact position which corresponds to the closed position. Moreover, advantageously, during the movement of the closing element 19 from the home position to the closed position, the closing element 19 also reaches an intermediate position which is located between the first contact position and the second contact position.

[0050] In the home position, both the first contact portion 20, and the second contact portion 21, are spaced apart from the flange 4. When the closing element 19 reaches the first contact position, in use, only the first contact portion 20 makes contact with the flange 4 (with the upper sheet 3 interposed between them). In use, in contrast, only when the closing element 19 reaches the second contact position, the second contact portion 21 makes contact with the flange 4 (again with the upper sheet 3 interposed between them - Figure 35).

[0051] The first contact portion 20 is configured to perform, in use, during the movement of the closing element 19 from the first contact position to the second contact position, the entire folding of the flange 4 outwards to make it adopt the operating configuration (making the projecting elements 8 snap into place). In contrast, the second contact position 21 is configured to adopt in use the second contact position when the closing element 19 adopts the closed position. Advantageously, the first contact portion 20 is configured to perform, in use, the first folding of the flange 4 during the movement from the first contact position to the intermediate position (but this aspect will be described in more detail below).

[0052] Regarding the first contact portion 20, in the preferred embodiments, the first surface 57 is advantageously shaped to match the operating surface 56 of the closing frame 18.

[0053] Advantageously, the closing element 19 has a plurality of first contact portions 20 which are configured to couple, in use, to the flange 4 at a plurality of different positions along a perimetric extent of the flange 4 itself. For that purpose the first contact portions 20 are distributed around the exiting central axis 14.

[0054] In contrast, the second contact portion 21 is advantageously shaped to match the closing frame 18; in particular the second surface 58 is shaped to match the operating surface 56. In this case, when the closing element 19 is in the closed position, the second contact portion 21 and the closing frame 18 are coupled to each other to clamp, in use, the flange 4 and the upper sheet 3 in order to fix them to each other thereby closing the tray 2. In the embodiments illustrated there is a single second contact portion 21 which extends without interruption around the exiting central axis 14; however, in other embodiments it may comprise a plurality of parts which are separate from each other.

[0055] In the preferred embodiments, the above-mentioned heating means are configured to heat the second contact portion 21.

[0056] In the preferred embodiments, the closing element 19 comprises a first member 24 and a second member 25 which are separate elements and which are movable one relative to the other parallel to the exiting central axis 14. In the embodiment illustrated, the first member 24 and the second member 25 are movable together with each other during the movement of the closing element 19 between the home position and the intermediate position, whilst the first member 24 and the second member 25 are movable one relative to the other (in particular, the second member 25 is movable relative to the first member 24 which remains fixed and stationary relative to the supporting element 12) during the movement of the closing element 19 between the intermediate position and the closed position. In more detail, when the closing element 19 reaches the intermediate position, the first member 24 couples to the supporting element 12, and remains coupled to the supporting element 12 during the subsequent movement of the closing element 19 from the intermediate position to the closed position, whilst the second member 25 couples to the supporting element 12 when the closing element 19 reaches the closed position.

[0057] In particular, the first member 24, one of whose embodiments is shown in the detail in Figures 14 to 17 and another in Figures 34 and 35, defines the first contact portion 20 (the first contact portions 20 in the accompanying figures), whilst the second member 25, one of whose embodiments is shown in the detail in Figures 10 to 13, defines the second contact portion 21.

[0058] In more detail, in the embodiments illustrated, the first member 24 advantageously comprises a plurality of projections 26 and each projection 26 defines one of the first contact portions 20. Moreover, the second member 25 preferably has a plurality of recesses 27. Each projection 26 of the first member 24 is movable inside a recess 27 of the second member 25, at least during part of the movement of the closing element 19, and at least during part of the movement of the closing element 19 from the first contact position to the closed position. Advantageously, each projection 26 is movable in a recess 27 during the movement of the closing element 19 from the second contact position to the closed position in the embodiment of Figures 9 to 33, and during the movement of the closing element 19 from the intermediate position to the closed position in the embodiment of Figures 34 and 35. In the preferred embodiments, each projection 26 enters the corresponding recess 27 after the closing element 19 has reached the intermediate position and the first member 24 has stopped against the supporting element 12.

[0059] In the embodiment illustrated, the first member 24 also comprises a first main body 28 which advantageously substantially has the shape of a parallelepiped. In particular, in the first main body 28 two first main faces 29 can be identified, each of which extends in a plane perpendicular to the exiting central axis 14, and four first lateral faces 30 which are opposite each other in pairs. In more detail, the projections 26 project relative to the first main body 28. In particular, the first member 24 comprises a pair of projections 26 for each of the first lateral faces 30 of the first main body 28. For example, the first member 24 comprises eight projections 26, as shown in Figures 14 and 15. Moreover, the first member 24 has at least one first through hole 31 which is threaded and which extends between the two first main faces 29. In more detail, the first member 24 has a plurality of first through holes 31 which extend between the two first main faces 29. Advantageously, those first through holes 31 have a first line of extension which is parallel to the exiting central axis 14.

[0060] As is clearly visible from Figure 14, the first member 24 also has at least one first hollow 33, preferably a plurality, which is made on the first main face 29 directed towards the supporting element 12. Advantageously, each first hollow 33 is configured to receive, in use, a projecting element 8 of the tray 2 when the flange 4 of that tray 2 is in the operating configuration. That first hollow 33 allows the projecting element 8 to not make contact with the first main face 29 of the first member 24 directed towards the housing 13, and therefore allows the projecting element 8 to pass the movable upper portion 10 of the stop 9. Preferably, the first member 24 has a number of first hollows 33 equal to the number of projecting elements 8 of the tray 2.

[0061] In the case of the embodiment of Figures 34 and 35, the shape of the first member 24 may be identical to what was described above with the sole exception of the orientation of the first surface 57.

[0062] In contrast, the second member 25 preferably comprises a second main body 34, which also substantially has the shape of a parallelepiped and in which two second main faces 35 can be identified, each of which extends in a plane perpendicular to the exiting central axis 14, and four second lateral faces 36 which are opposite each other in pairs. Moreover, the second member 25 comprises an annular portion 37 which is fixed to the second main body 34 at the outer edge of the second main face 35 directed towards the supporting element 12, and which comprises the second contact portion 21. Advantageously, the second main body 34 and the annular portion 37 together define a concavity 38 which is directed towards the housing 13 defined by the supporting element 12 and is configured to receive the first member 24 at least when the closing element 19 is in the closed position as shown in Figure 25.

[0063] The recesses 27 are made in the second annular portion 37, advantageously at inner lateral faces which define the concavity 38. In the embodiments illustrated, the second member 25 has a pair of recesses 27 for each of the inner second lateral faces 36 of the annular portion 37. For example, the second member 25 has eight recesses 27, as shown in Figures 10 and 11. In the preferred embodiments, the number of recesses 27 is equal to the number of projections 26. For example, as can be seen in the figures, in the embodiment illustrated there are eight projections 26 and eight recesses 27, and each projection 26 is advantageously movable inside a respective recess 27.

[0064] As can be seen in the accompanying figures each recess 27 extends to the second surface 58 whose extent it limits locally. In these embodiments, preferably the second surface 58 does not have interruptions in its continuity in the zones in which it has a limited extent due to the recesses 27. That is advantageous since it allows the upper sheet 3 to be fixed along the entire annular extent of the flange 4 of the tray 2.

[0065] Advantageously, in the second member 25 there is at least one second through hole 39 which extends between the second main faces 35 of the second main body 34, substantially putting the concavity 38 in communication with the outside through the second main faces 35. As can be seen in particular from Figures 10 and 13, the second through hole 39 has, moving from the second main face 35 directed towards the housing 13, towards the other second main face 35, a narrowing of the cross-section. In particular, that narrowing is caused by a shoulder 40 which identifies an abutting surface 41: advantageously, the second through hole 39 comprises a first zone 42 and a second zone 43, the first zone 42 having a diameter greater than that of the second zone 43 and being interposed between the second zone 43 and the concavity 38.

[0066] Preferably, the second member 25 has a plurality of second through holes 39. Advantageously, those second through holes 39 have a second line of extension which is parallel to the exiting central axis 14 and which coincides with the first line of extension of the first through holes 31. Therefore, the first through holes 31 and the second through holes 39 are concentric and extend along the same line of extension.

[0067] In the embodiment illustrated, the closing machine 1 also comprises at least one connecting element and at least one elastic element, which are configured to connect to each other the first member 24 and the second member 25 of the closing element 19. In detail, the connecting element advantageously comprises a pin 44 and the elastic element is preferably constituted of a spring 45.

[0068] In particular, the connecting element (the pin 44) is configured to connect the first member 24 and the second member 25. Advantageously, the pin 44 comprises a central body 46 and a locking element 47. The central body 46 has a first end 48, which is threaded and is screwed into the first through hole 31 in such a way that the pin 44 is movable together with the first member 24, and a second end 49, to which the locking element 47 is fixed and which projects outwards from the second through hole 39. The locking element 47 is configured to prevent the pin 44 from slipping out of the second through hole 39 during the movement of the first member 24 relative to the second member 25 under the action of the elastic element. In the preferred embodiments, the closing machine 1 comprises a plurality of pins 44 and, in particular, comprises a pin 44 for each first through hole 31 and second through hole 39 which are aligned with each other.

[0069] In contrast, the elastic element (the spring 45) is positioned between the first member 24 and the second member 25. In more detail, the spring 45 has a third end 50, which abuts against the first main face 29 directed towards the second member 25, and a fourth end 51, which abuts against the abutting surface 41 previously defined. In the embodiment illustrated, the spring 45 is positioned around the pin 44. Preferably, the closing element 19 comprises a plurality of springs 45 and, in particular, a spring 45 for each pin 44. In particular, the spring 45 is configured to adopt a compressed configuration and an extended configuration. The spring 45 switches its configuration from the extended configuration to the compressed configuration during the movement of the closing element 19 between the home position and the closed position, when the second member 25 moves relative to the first member 24 coupled to the supporting element 12. In contrast, when the closing element 19 moves from the closed position towards the home position, the spring 45 causes shifting of the first member 24 relative to the second member 25 holding it coupled to the supporting element 12 until the closing element 19 returns to the intermediate position.

[0070] In the preferred embodiments, the closing machine 1 also comprises a cutting element 52 which is configured to cut, in use, the upper sheet 3. In detail, the cutting element 52 is movable between a retracted position, in which the cutting element 52 is, in use, spaced apart from the upper sheet 3 and an extracted position. Preferably, the movement of the cutting element 52 from the retracted position to the extracted position causes, in use, cutting of the upper sheet 3. The cutting element 52 is movable from the retracted position to the extracted position when the closing element 19 is in the closed position. That is advantageous because, when the closing element 19 is in the closed position, the upper sheet 3 and the flange 4 are clamp between the second contact portion 21 and the closing frame 18, thereby holding the upper sheet 3 in the correct position and allowing the cutting.

[0071] In the embodiment illustrated, the cutting element 52 is fixed to the closing element 19 during the movement of the closing element 19 between the home position and the closed position, whilst it is movable relative to the closing element 19 when the latter is in the closed position. In the retracted position, the cutting element 52 does not project relative to the closing element 19, whilst it projects when it is in the extracted position.

[0072] The following is a schematic description of preferred operation of the closing machine 1 which corresponds to the implementation of several steps of the method according to this invention described below.

[0073] First, the movement of the closing element 19 from the home position to the closed position will be described, which is substantially closing of the closing machine 1, whilst then the movement of the closing element 19 from the closed position to the home position will be described, which is substantially opening of the closing machine 1. The description which follows will refer to Figures 20 to 32 and 34 to 35, in which, however, the product is not shown placed inside the tray 2 in order to make the structural aspects of the closing machine 1 appear clearer.

[0074] Initially, the closing element 19 is in the home position (Figure 20 and 34) and is therefore spaced apart from the supporting element 12. When the closing element 19 is in the home position, the projections 26 of the first member 24 are spaced apart from the recesses 27 of the second member 25 and the cutting element 52 is in the retracted position. Moreover, the springs 45 are in an extended configuration. Since the closing element 19 and the supporting element 12 are spaced apart from each other, the tray 2 with the flange 4 in the initial configuration (that is to say, the configuration shown in Figures 1 to 4) is inserted inside the housing 13 defined by the supporting element 12. The upper sheet 3 is positioned over the tray 2; for that purpose the closing machine 1 may comprise suitable positioning means for the upper sheet 3 and / or retaining means for retaining the upper sheet 3 over the tray 2, which are known in themselves and therefore not described in detail. Then, the closing element 19 is moved parallel to the exiting central axis 14, until it reaches the first contact position (Figure 21) in which the first contact portions 20 make contact with the flange 4 (with interposition of the upper sheet 3). During this movement, the first member 24 and the second member 25 are moved together with each other: the projections 26 are therefore still spaced apart from the recesses 27 and the springs 45 remain in the extended configuration. Moreover, the flange 4 of the tray 2 remains in the initial configuration and the cutting element 52 is held in the retracted configuration. The movement of the closing element 19 then continues towards the closed position, and the first contact portions 20 act on the flange 4 folding it. In fact, the closing element 19 is moved towards the closed position until it reaches the intermediate position (Figure 23 and 34), in which the first member 24 couples to the supporting element 12 (abuts against it with the flange 4 and the upper sheet 3 interposed between the two elements). When the closing element 19 is in the intermediate position, the projections 26 of the first member 24 are still spaced apart from the recesses 27 made in the second member 25, the springs 45 are in the extended configuration and the cutting element 52 is in the retracted position.

[0075] In more detail, in the case of the embodiment of Figures 9 to 33, during the passage from the first contact position to the intermediate position the first contact portions 20 cause a first folding of the flange 4 outwards, to make the flange 4 adopt the intermediate configuration between the initial configuration and the final configuration, as previously described. Once the intermediate position is reached the first folding of the flange 4 ends.

[0076] Or, in the case of the embodiment of Figures 34 and 35, during the passage from the first contact position to the intermediate position the first contact portions 20 cause the entire folding of the flange 4 outwards, to make the flange 4 adopt the final configuration, as previously described. Therefore, once the intermediate position is reached the folding of the flange 4 ends.

[0077] Then, the movement of the closing element 19 continues until the second contact position is reached (Figure 24). During this movement, the second member 25 moves towards the first member 24 and the springs 45 gradually switch their configuration from the extended configuration to an increasingly compressed configuration. The projections 26 are inserted inside the recesses 27, whilst the cutting element 52 is still in the retracted position.

[0078] In the case of the embodiment of Figures 34 and 35, in which the closed position corresponds to the second contact position, the movement of the closing element 19 is ended.

[0079] Or, in the case of the embodiment of Figures 9 to 33, the closing element 19 is then moved from the second contact position to the closed position (Figure 25), and the second contact portion 21 performs the second folding of the flange 4 of the tray 2 outwards, until the flange 4 adopts its operating configuration. During the movement to the closed position, the first member 24 enters increasingly further inside the concavity 38 of the second member 25 and the springs 45 reach a maximum compression configuration. The projections 26 are fully inserted inside the recesses 27, whilst the cutting element 52 is still in the retracted position.

[0080] When the closed position is reached, the closing frame 18 and the second contact portion 21 clamp between them the upper sheet 3 and the flange 4 of the tray 2 in the operating configuration. The heating produced by the heating means causes the upper sheet 3 to adhere to the flange 4.

[0081] Whilst the closing element 19 is held in the closed position, the cutting element 52 is moved from the retracted position to the extracted position to cut the excess upper sheet 3 (Figure 26).

[0082] In contrast, regarding opening of the closing machine 1, during the movement of the closing element 19 from the closed position to the intermediate position, the springs 45 push the first member 24 away from the second member 25 which is moving away from the supporting element 12, with a relative sliding of the projections 26 (which remain stationary relative to the supporting element 12) and the recesses 27 (which in contrast move together with the second member 25). In contrast, during the subsequent movement from the intermediate position to the home position, the first member 24 and the second member 25 are movable together with each other, as previously described for closing of the closing machine 1.

[0083] It should be emphasised that in the preferred embodiments, the movement of the closing element 19 from the home position to the closed position, and vice versa, occurs substantially continuously without any interruption. In contrast, it is preferable for the closing element 19 to hold the closed position for a predetermined time, in order to guarantee good quality adhesion of the upper sheet 3 to the flange 4.

[0084] Below is a description of the method for packaging a product in a container according to this invention. The container comprises a tray 2, which in turn comprises a bottom wall 5, a plurality of lateral walls 6 and a flange 4 connected to the top of the lateral walls 6, and an upper sheet 3 applied to an upper surface 32 of the flange 4. In accordance with what was described above, fixed to the flange 4 of the tray 2 there is at least one projecting element 8 and at least one of the lateral walls 6 of the tray 2 comprises at least one stop 9 configured to bend inwards towards the inside of the tray 2; moreover, in the initial configuration of the flange 4, the stop 9 is at least partly superposed on the projecting element 8 inside the tray 2.

[0085] That method may be at least partly advantageously implemented using a closing machine 1 of the type described above, for example the closing machine 1 illustrated in the figures. Again, it should be emphasised that the product is not shown in the figures.

[0086] First, the method comprises a pick-up step in which the tray 2 is picked up with the flange 4 placed in the initial configuration as previously described, that is to say, with the flange 4 extending upwards from the lateral walls 6 away from the bottom wall 5.

[0087] Similarly to the prior art methods, the method according to this invention also comprises both an inserting step, in which the product is inserted into the inner space 54 of the tray 2, and a subsequent positioning step, in which the upper sheet 3 is positioned over the tray 2 and the product. The inserting step may be performed either before or after the pick-up step; however, in some cases, it is possible that the inserting step is performed simultaneously with the pick-up step

[0088] The method also comprises both a coupling step and a fixing step.

[0089] In the coupling step, the upper sheet 3 is pressed and is held pressed against the flange 4 of the tray 2. In contrast, in the fixing step, which is carried out during the coupling step, while the upper sheet 3 is held pressed against the upper surface 32 of the flange 4, the upper sheet 3 is fixed to the upper surface 32 of the flange 4. In this way the upper sheet 3 is fixed to the flange 4 of the tray 2 so that the product is contained between the tray 2 and the upper sheet 3. The container is obtained as a result of carrying out the fixing step. Advantageously, in the known way, the fixing step is carried out by heating the upper sheet 3 in such a way as to make it stick to the flange 4.

[0090] According to a further innovative aspect of this invention, the method also comprises a folding step which is carried out during the coupling step. During the folding step the flange 4 is folded outwards from the tray 2 relative to the lateral walls 6, so as to switch it from the initial configuration to the operating configuration in which, as previously described, the flange 4 is folded outwards from the tray 2. Moreover, during the folding step, by means of folding of the flange 4, the projecting element 8 is folded and the stop 9 bends inwards towards the inside of the tray 2. Then, again by means of folding of the flange 4 (and the consequent movement of the projecting element and the deformation of the stop), the projecting element 8 is made to pass beyond the stop 9, allowing the stop 9 to elastically snap into place and substantially return to the position which it occupied before the folding step.

[0091] In some embodiments (for example the one implementable with the closing machine of Figures 34 and 35), there is a single folding step.

[0092] In other embodiments, such as the one of Figures 9 to 33, the folding step advantageously comprises, in order, a first folding sub-step and a second folding sub-step. During the first folding sub-step a first folding of the flange 4 of the tray 2 outwards is performed, to make it adopt the intermediate configuration between the initial configuration and the operating configuration, as previously described. In contrast, during the second folding sub-step a second folding of the flange 4 outwards is performed, starting from the intermediate configuration, to make it adopt the operating configuration. In the preferred embodiments, the tray 2 has a main axis 53 . That main axis 53 is defined as the axis which extends starting from the bottom wall 5, which comes out of the inner space 54 of the tray 2, and which is substantially centred relative to the lateral walls 6 of the tray 2. When the tray 2 is inserted into the housing 13 of the closing machine 1, the main axis 53 coincides with the exiting central axis 54.

[0093] In particular, in the initial configuration the upper surface 32 of the flange 4 forms an initial angle with the main axis 53. That initial angle is measured from the upper surface 32 of the flange 4 to the main axis 53 inside the tray 2 (in other words, it is measured in a similar way to what was described above for the first angle 100 and the second angle 101, 102). When the first folding sub-step is required, during its execution the first folding of the flange 4 is performed until an intermediate angle is reached between the upper surface 32 of the flange 4 and the main axis 53 which is greater than the initial angle and less than 90°, whilst during the second folding sub-step the second folding of the flange 4 is performed until an operating angle is reached between the upper surface 32 of the flange 4 and the main axis 53 which is greater than 90°.

[0094] If a folding step which is not split into two sub-steps is required, preferably during its execution the flange 4 is folded until the operating angle which is greater than 90° is reached.

[0095] Advantageously, the operating angle is between 90° and 150°, preferably between 100° and 140°, and even more preferably between 110° and 130°. For that purpose, advantageously a closing machine 1 as described above may be used, in which the operating surface 56 of the closing frame 18 forms, relative to the exiting central axis 14, a first angle 100 which is between 90° and 150°, preferably between 100° and 140°, even more preferably between 110° and 130°, (inclined outwards relative to the exiting central axis 14). In that case, during the folding step the flange 4 is folded until it rests on the operating surface 56 of the closing frame 18. Moreover, at the end of the folding step and during the fixing step the closing element 19 is in the closed position and clamps the flange 4 and the upper sheet 3 against the operating surface 56 of the closing frame 18.

[0096] At the end of the coupling step, the method comprises a releasing step, which is carried out after the fixing step, in which the flange 4 is released. During this releasing step, the flange 4 moves towards the initial configuration until the projecting element 8 abuts against the top of the stop 9. In this case, as a result of the releasing step, the flange 4 is held in the final configuration, since the stop 9 prevents the projecting element 8 and the flange 4 as a whole from returning to the initial configuration.

[0097] Advantageously, the method also comprises a cutting step, in which the excess upper sheet 3 is cut, which is carried out after the start of the coupling step. In some cases, the cutting step is carried out after the fixing step; in other cases, the cutting step is carried out simultaneously with the fixing step; in yet other cases the cutting step is in contrast carried out before the fixing step.

[0098] In some embodiments of this invention, the positioning, coupling, fixing and folding steps are carried out by a closing machine 1 of one of the types described above (depending on the embodiments of the method to be adopted).

[0099] Therefore, in general, the closing machine comprises the supporting element 12 which defines the housing 13 and the closing element 19 which is operatively associated with the supporting element 12 and which is movable relative to the supporting element 12 between the home position and the closed position. The coupling, fixing and folding steps are carried out by means of the movement of the closing element 19 from the home position to the closed position.

[0100] Advantageously the closing element 19 comprises the first contact portion 20 and the second contact portion 21, and during the movement of the closing element 19 from the home position to the closed position, one after another, the closing element 19 is brought into the first contact position, in which the first contact portion 20 couples to the flange 4, and into the second contact position, in which the second contact portion 21 couples to the flange 4.

[0101] In some embodiments, during the movement of the closing element 19 from the first contact position to the second contact position, using the first contact portion 20 the first folding sub-step for folding the flange 4 outwards is carried out to make it adopt the intermediate configuration between the initial configuration and the operating configuration. Then, during the movement of the closing element 19 from the second contact position to the closed position, using the second contact portion 21 the second folding sub-step for folding the flange 4 outwards is carried out to make it adopt the operating configuration. This embodiment may for example be carried out using the closing machine 1 of Figures 9 to 33.

[0102] In contrast, in other embodiments, during the movement of the closing element 19 from the first contact position to the second contact position, the entire folding step for folding the flange 4 outwards is carried out, to make it adopt the operating configuration, advantageously using only the first contact portion 20. This embodiment may for example be carried out using the closing machine 1 of Figures 34 and 35.

[0103] The fixing step is advantageously carried out by heat-sealing the upper film 3 to the flange 4 using the second contact portion 21.

[0104] Again with reference to the closing machine 1 described above, in which the closing element 19 comprises the first member 24 and the second member 25, during the movement of the closing element 19 between the home position and an intermediate position located between the first contact position and the second contact position, the first member 24 and the second member 25 move together with each other, whilst during the movement between the intermediate position and the closed position, the second member 25 moves relative to the first member 24.

[0105] As already explained relative to the closing machine, when the closing element 19 reaches the intermediate position, the first member 24 is coupled to the supporting element 12. The first member 24 is then held coupled to the supporting element 12 during the subsequent movement from the intermediate position to the closed position. In contrast, the second member 25 couples to the supporting element 12 when the closing element 19 reaches the closed position.

[0106] This invention brings important advantages.

[0107] In fact, thanks to this invention, it was possible to provide both a closing machine and a method for packaging a product in a container comprising a tray and an upper sheet which allow a reduction in production times for making a container compared with the prior art.

[0108] Moreover, both a closing machine and a method were provided for packaging a product in a container comprising a tray and an upper sheet which do not require the use of specific folding machines, thereby simplifying the production process.

[0109] Finally, it should be noticed that this invention is relatively easy to produce and that even the cost linked to implementing the invention is not very high. The invention described above may be modified and adapted in several ways without thereby departing from its scope as defined by the attached claims.

[0110] All details may be substituted with other technically equivalent elements and the materials used, as well as the shapes and dimensions of the various components, may vary according to requirements.

Claims

1. A method for packaging a product, comprising the following steps: a pick-up step, in which a tray (2) comprising a bottom wall (5), a plurality of lateral walls (6) and a flange (4) connected to the top of the lateral walls (6) is picked up, the bottom wall (5) and the lateral walls (6) delimiting an inner space (54) of the tray (2) and the flange (4) being placed in an initial configuration in which it extends upwards from the lateral walls (6) away from the bottom wall (5) of the tray (2), the tray (2) also comprising at least one projecting element (8) fixed to the flange (4) and at least one of the lateral walls (6) comprising at least one stop (9) which is configured to bend inwards towards the inside of the tray (2) and which, in the initial configuration of the flange (4), is at least partly superposed on the at least one projecting element (8), inside the tray (2); an inserting step in which the product is inserted into the inner space (54) of the tray (2); a positioning step, in which an upper sheet (3) is positioned over the tray (2) and the product; a coupling step, in which the upper sheet (3) is pressed and is held pressed against the flange (4) of the tray (2); a fixing step, which is carried out during the coupling step, in which the upper sheet (3) is fixed to an upper surface (32) of the flange (4) to obtain the container; and a folding step, carried out during the coupling step, during which the flange (4) is folded outwards from the tray (2) relative to the lateral walls (6), to switch it from the initial configuration to an operating configuration in which the flange (4) is folded outwards from the tray (2). wherein, moreover, during the folding step, by means of folding of the flange (4), in order: the at least one projecting element (8) is folded, bending inwards towards the inside of the tray (2) the at least one stop (9) at least partly superposed on the at least one projecting element (8); and the at least one projecting element (8) is made to pass beyond the at least one stop (9), allowing the at least one stop (9) to elastically snap into place and substantially return to a position which it occupied before the folding step.

2. The method according to claim 1, wherein the tray (2) has a main axis (53) which extends starting from the bottom wall (5), which comes out of the inner space (54) of the tray (2), and which is substantially centred relative to the lateral walls (6) of the tray (2), and wherein: in the initial configuration the upper surface (32) of the flange (4) forms an initial angle with the main axis (53) which is less than 90°; and during the folding step the flange (4) is folded until an operating angle is reached between the upper surface (32) of the flange (4) and the main axis (53) which is greater than 90°.

3. The method according to claim 2, wherein, during the folding step, the flange (4) is folded until an operating angle is reached which is between 90° and 150°, preferably between 100° and 140°, even more preferably between 110° and 130°.

4. The method according to claim 1, 2 or 3, wherein the folding step comprises, in order, a first folding sub-step and a second folding sub-step, and wherein: during the first folding sub-step a first folding of the flange (4) of the tray (2) outwards is performed, to make it adopt an intermediate configuration between the initial configuration and the operating configuration; and during the second folding sub-step a second folding of the flange (4) outwards is performed, to make it adopt the operating configuration.

5. The method according to claim 4 when it depends on 2, wherein: during the first folding sub-step the first folding of the flange (4) is performed until an intermediate angle is reached between the upper surface (32) of the flange (4) and the main axis (53) which is greater than the initial angle and less than 90°; and during the second folding sub-step the second folding of the flange (4) is performed until the operating angle is reached between the upper surface (32) of the flange (4) and the main axis (53).

6. The method according to any one of claims 1 to 5, also comprising a releasing step carried out after the fixing step, in which the flange (4) is released, during the releasing step the flange (4) moving towards the initial configuration until the at least one projecting element (8) abuts against the top of the at least one stop (9).

7. The method according to any one of claims 1 to 6, also comprising a cutting step, carried out after the start of the coupling step, in which the excess upper sheet (3) is cut.

8. The method according to any one of claims 1 to 7, wherein the positioning, coupling, fixing and folding steps are carried out by a closing machine which comprises: - a supporting element (12) which defines a housing (13) having an exiting central axis (14), into which the tray (2) is inserted before the positioning step; and - a closing element (19) which is operatively associated with the supporting element (12) and which is movable relative to the supporting element (12), parallel to the exiting central axis (14), between a home position, in which the closing element (19) and the supporting element (12) are spaced apart and uncoupled from each other, and a closed position, in which the closing element (19) and the supporting element (12) are coupled to each other; wherein, moreover, the coupling, fixing and folding steps are carried out by means of the movement of the closing element (19) from the home position to the closed position.

9. The method according to claim 8, wherein a closing machine is used in which the closing element (19) comprises a first contact portion (20) and a second contact portion (21) which are configured to couple to the flange (4) during the movement of the closing element (19) from the home position to the closed position, and wherein during the movement of the closing element (19) from the home position to the closed position, one after another, the closing element (19) is brought into a first contact position, in which the first contact portion (20) couples to the flange (4), and into a second contact position, in which the second contact portion (21) couples to the flange (4).

10. The method according to claim 9 when it depends on claim 4, wherein, during the movement of the closing element (19) from the first contact position to the second contact position, using the first contact portion (20) the first folding sub-step for folding the flange (4) outwards is carried out to make it adopt the intermediate configuration between the initial configuration and the operating configuration, and, during the movement of the closing element (19) from the second contact position to the closed position, using the second contact portion (21) the second folding sub-step for folding the flange (4) outwards is carried out to make it adopt the operating configuration.

11. The method according to claim 9, wherein, during the movement of the closing element (19) from the first contact position to the second contact position, the folding step for folding the flange (4) outwards is carried out to make it adopt the operating configuration.

12. The method according to any one of claims 9 to 11, wherein the fixing step is carried out by heat-sealing the upper film (3) to the flange (4) using the second contact portion (21).

13. The method according to any one of claims 8 to 12, wherein a closing machine is used in which the closing element (19) comprises a first member (24) which defines the first contact portion (20), and a second member (25) which defines the second contact portion (21), the first member (24) and the second member (25) being separate elements and being movable one relative to the other parallel to said exiting central axis (14), and wherein: during the movement from the home position to the closed position, the closing element (19) is also brought into an intermediate position which is located between the first contact position and the second contact position; during the movement between the home position and the intermediate position, the first member (24) and the second member (25) move together with each other; and during the movement between the intermediate position and the closed position, the second member moves relative to the first member (24).

14. The method according to claim 13, wherein, when the closing element (19) reaches the intermediate position, the first member (24) couples to the supporting element (12), wherein the first member (24) is held coupled to the supporting element (12) during the movement from the intermediate position to the closed position, and wherein the second member (25) couples to the supporting element (12) when the closing element (19) reaches the closed position.

15. The method according to any one of claims 8 to 14, wherein a closing machine is used in which the supporting element (12) has a closing frame (18) which delimits the top of the housing (13) and which has an operating surface (56) which forms, relative to the exiting central axis (14), a first angle (100) which is between 90° and 150°, preferably between 100° and 140°, even more preferably between 110° and 130°, and which is inclined outwards relative to the exiting central axis (14); wherein during the folding step the flange (4) is folded until it rests on the operating surface (56) of the closing frame (18) and wherein, at the end of the folding step and during the fixing step the closing element (19) is in the closed position and clamps the flange (4) and the upper sheet (3) against the operating surface (56) of the closing frame (18).