Tray for holding a food product

Description

[0001] The present invention relates to the field of food packaging.

[0002] It relates more particularly to a tray intended to contain a foodstuff. It also relates to a method of manufacturing such a tray.

[0003] In the field of food packaging, the foodstuff to be consumed is generally placed in a tray consisting of an outer cardboard shell and an inner envelope formed of a plastic film covering the outer shell internally. The inner envelope can be secured to the outer shell by thermoforming. For this purpose, adhesion zones are advantageously provided on the inner periphery of the outer shell, said adhesion zones being capable of being in contact with the plastic film during a step of shaping the inner envelope. These adhesion zones are generally made of a thermo-adhesive coating which is heat-activatable. By locally heating the plastic film at the areas in contact with the thermo-adhesive coating, the adhesive power of said coating is activated, which allows the plastic film to adhere to the outer shell.Such trays have been described in particular in documents EP 0 604 507 A1, US 3 512 332 A, US 2019 / 359375 A1 and DE 87 15 562 U1.

[0004] In the manufacturing processes currently used to form such trays, the step of thermoforming the plastic film requires the use of a thermoforming mold inside which the outer shell is placed. Since the outer shell is generally obtained by folding a pre-cut cardboard blank onto itself, it is necessary to stabilize the blank in a pre-assembled configuration corresponding to the final shape of the outer shell before its introduction into the mold. This makes it possible in particular to prevent the outer shell from coming out of the mold due to the natural tendency of the blank to return to its original flat configuration. This stabilization is generally carried out by applying a layer of quick-setting glue to several surfaces of the blank intended to be superimposed on each other in the pre-assembled configuration of the blank. This application of quick-setting glue, however, has many disadvantages.On the one hand, it generates an additional manufacturing step, making the entire manufacturing process more complex to implement. On the other hand, it increases the manufacturing cost of the tray due to this additional use of quick-setting glue. In addition, this application of quick-setting glue can generate soiling phenomena on the trays and on the manufacturing machines, which requires frequent cleaning and maintenance operations. Manufacturing rates are therefore reduced as a result.

[0005] The invention therefore aims to propose a tray and a method of manufacturing such a tray which does not have the aforementioned drawbacks.

[0006] To this end, the invention relates to a tray, in particular for packaging a foodstuff, comprising: an outer shell comprising at least one bottom wall and at least one side wall, an inner envelope formed from a plastic film internally covering the outer shell while being in contact at least partially with said at least one side wall, the inner envelope being secured to said at least one side wall at a plurality of adhesion zones arranged on an internal face of said at least one side wall, characterized in that each of the adhesion zones is completely surrounded by a thicker portion of said at least one side wall and in that the outer shell is formed from a pre-cut blank, preferably made of cardboard, which is folded back on itself, said blank having assembly tabs provided with a through opening and folding flaps intended to be folded back onto said assembly tabs, the thicker portions of said at least one side wall being formed by the superposition of parts of the assembly tabs which are covered by said folding flaps and parts of the folding flaps which cover the assembly tabs, the adhesion zones corresponding to the portions of the folding flaps which are arranged opposite the through openings of the assembly tabs.

[0007] In a particular configuration of the invention, the adhesion zones have a circular shape.

[0008] In another particular configuration of the invention, said at least one bottom wall has an octagonal shape.

[0009] In another particular configuration of the invention, the internal envelope is made of a thermoplastic film which is secured to the external shell by heat sealing.

[0010] In another particular configuration of the invention, the outer shell is formed of two half-shells connected to each other by a hinge, each of the half-shells comprising a bottom wall and a side wall.

[0011] In another particular configuration of the invention, the hinge is formed by a folding edge of the blank.

[0012] In another particular configuration of the invention, the two half-shells have identical or substantially identical shapes.

[0013] In another particular configuration of the invention, the bottom wall of each of the half-shells has an octagonal shape.

[0014] In another particular configuration of the invention, the inner envelope comprises a peripheral edge projecting from the outer shell, said peripheral edge being provided with a first V-shaped groove and a second V-shaped groove, said first and second grooves being arranged on either side of the hinge of the outer shell and together forming a hinge element for the inner envelope.

[0015] The invention also relates to a method of manufacturing a tray as defined above, the method comprising the following steps: providing a pre-cut blank, preferably made of cardboard, in a flat configuration, said blank being covered in several areas, called adhesion areas, with a thermo-adhesive coating; providing a plastic film; folding the blank onto itself in a pre-assembled configuration, in which the blank forms an external shell comprising at least one bottom wall and at least one side wall, and in which the adhesion areas are arranged on an internal face of said at least one side wall, each being completely surrounded by two superimposed portions of the blank; introducing the external shell thus obtained into a thermoforming mold; introducing the plastic film into the thermoforming mold; closing the thermoforming mold;heating and shaping the plastic film so as to form an internal envelope internally covering the external shell while being in contact at least partially with said at least one side wall at the level of the plurality of adhesion zones; applying heat at the level of the adhesion zones so as to activate the thermo-adhesive coating and, thus, achieve a bonding of the internal envelope to the external shell at the level of said adhesion zones, the internal envelope thus preventing the blank from returning to its flat configuration;

[0016] In a particular configuration of the invention, the blank comprises a central zone delimited at least by two longitudinal edges, respectively lower and upper, and by at least two lateral edges, respectively left and right, the central zone being extended on each of said longitudinal and lateral edges by a folding flap, at least two of said folding flaps being provided with adhesion zones and at least two other of said folding flaps being extended at each of their ends by an assembly tab provided with a through opening, said through openings being positioned so as to be arranged opposite the adhesion zones in the pre-assembled configuration of the blank.

[0017] In a particular configuration of the invention, the blank comprises two identical parts separated by a folding edge, each of the parts being intended to form a half-shell of the external shell after folding the blank and the folding edge being intended to form a hinge connecting the two half-shells together.

[0018] In a particular configuration of the invention, each of the parts comprises a central zone delimited at least by two longitudinal edges, respectively lower and upper, and by at least two lateral edges, respectively left and right, the central zone being extended on each of said longitudinal and lateral edges by a folding flap, at least two of said folding flaps being provided with adhesion zones and at least two other of said folding flaps being extended at each of their ends by an assembly tab provided with a through opening, said through openings being positioned so as to be arranged opposite the adhesion zones in the pre-assembled configuration of the blank.

[0019] In another particular configuration of the invention, the central zone has an octagonal shape.

[0020] In another particular configuration of the invention, the thermoforming mold comprises retaining means capable of retaining the external shell inside the mold before closing the mold.

[0021] In another particular configuration of the invention, said retaining means comprise a plurality of punches intended to locally deform an external face of the external shell.

[0022] In another particular configuration of the invention, the step of applying heat to the adhesion zones is carried out by means of electrodes producing ultrasound.

[0023] In another particular configuration of the invention, the thermo-adhesive coating consists of a PVA varnish.

[0024] The invention will be better understood upon reading the non-limiting description which follows, given with reference to the attached figures. Figure 1 is a perspective view of a tray according to a first embodiment of the invention; Figure 2 is a view of a pre-cut blank intended to form the outer shell of the tray of the Figure 1 , the blank being in its flat configuration; Figure 3 is a view of the side of the Figure 2 after a first folding step; Figure 4 is a view of the side of the Figure 2 after a second folding step; Figure 5 is a view of the side of the Figure 2 after a third folding step, said blank then being in its pre-assembled configuration; Figure 6 is a perspective view of a thermoforming mold for thermoforming a plastic film onto the blank of the Figure 5 ; Figure 7 is a view of the tray of the invention during a step of heat-sealing the adhesion zones; Figure 8 is a perspective view of a tray according to a second embodiment of the invention; Figure 9 is a view of a pre-cut blank intended to form the outer shell of the tray of the Figure 8 , the blank being in its flat configuration; Figure 10 is a view of the side of the Figure 9 in its pre-assembled configuration.

[0025] In reference to the Figure 1 , a tray 10 according to a first embodiment of the invention is shown in an open position. This tray 10 defines an interior storage space for a foodstuff. It comprises an outer shell 11, for example made of cardboard, and an inner envelope 12 formed of a plastic film internally covering the outer shell 11. The outer shell 11 is formed of two half-shells 11a, 11b connected together by a fold line forming a hinge 13, the two half-shells having identical or substantially identical shapes. The hinge 13 makes it possible to move from the open position shown in the Figure 1 in a closed position (not shown) of the outer shell 11, in which one of the half-shells 11a or 11b is folded against the other half-shell 11a, 11b having pivoted around the hinge 13. Each of the half-shells 11a, 11b comprises an octagonal-shaped bottom wall 111 and a side wall 112 completely surrounding the bottom wall 111 and which is substantially perpendicular thereto. The inner casing 12 is in at least partial contact with the side wall 112 and with the bottom wall 111 of each of the half-shells 11a, 11b. Preferably, the internal envelope 12 will completely match the internal shape of the external shell 11. The internal envelope 12 is secured to the side wall 112 of each of the half-shells 11a, 11b at a plurality of adhesion zones 14 arranged on an internal face of said side wall 112.These adhesion zones 14 have a circular shape and are made of a thermo-adhesive coating, which is activated under the effect of heat. The inner casing 12 comprises a peripheral edge 15 projecting from the outer shell 11 and arranged mainly in a plane parallel to the bottom wall 111. The peripheral edge 15 is provided with a first groove 16 with a V-shaped profile and a second groove 17 with a V-shaped profile, said grooves 16, 17 being arranged on either side of the hinge 13 of the outer shell 11. These grooves 16, 17 together form a hinge element for the inner casing 12.

[0026] In reference to the Figure 2 , there is shown a pre-cut and pre-folded cardboard blank 20 which is intended to form the external shell 11 of the tray 10 of the Figure 1 . This blank 20 comprises two identical parts 21, 22 separated by a folding edge 13, each of the parts 21, 22 comprising a central zone, respectively 210, 220, of octagonal shape delimited by a lower longitudinal edge, respectively 211, 221, by an upper longitudinal edge, respectively 213, 223, by a left lateral edge, respectively 212, 222, and by a right lateral edge, respectively 214, 224. The lower longitudinal edges 211, 221, respectively upper 213, 223, are connected respectively to the left lateral edges 212, 222 and right 214, 224 by two lower oblique edges left 215, 225 and right 217, 227, and by two upper oblique edges left 216, 226 and right 218, 228.

[0027] The central zones 210, respectively 220, are extended on each of their longitudinal and lateral edges by a folding flap, namely a lower folding flap 231, respectively 241, an upper folding flap 233, respectively 243, a left folding flap 232, respectively 242, and a right folding flap 234, respectively 244. The lower and upper longitudinal edges 211 and 213, respectively 221 and 223, and the left and right lateral edges 212 and 214, respectively 222 and 224, correspond to folding edges of the pre-folded blank 20 so as to allow the folding of the folding flaps 231-234, respectively 241-244, in a vertical position, perpendicular to the central zone 210, respectively 220.The lower and upper folding flaps 231, 233 and 241, 243 are provided on their inner face with two circular zones 14 covered with a thermo-adhesive coating, each of said circular zones 14 being close to one of the end edges of said folding flaps 231, 233, respectively 241, 243, which adjoins one of the oblique edges 215-218, respectively 225-228. In addition, the left and right folding flaps 232, 234, respectively 242, 244, are extended on each of their end edges 239, respectively 249, which adjoin the oblique edges 215-218, respectively 225-228, by an assembly tab 235, respectively 245.Each of the assembly tabs 235, respectively 245, comprises a first portion 235a, respectively 245a, of trapezoidal shape connected to one of the left or right folding flaps 232, 234, respectively 242, 244, at one of the end edges 239, respectively 249, and a second portion 235b, respectively 245b, connected to the first portion 235a, respectively 245a, by a fold line. The end edges 239, respectively 249, correspond to folding edges of the pre-folded blank 20 so as to allow the assembly tabs 235, respectively 245, to be folded into a folded position in which they are oriented obliquely relative to the left and right folding flaps 232, 234, respectively 242, 244.The second part 235b, respectively 245b, of the assembly tabs 235, respectively 245, is provided with a through opening 18, said through openings 18 having a circular shape substantially identical to that of the circular zones 14.

[0028] In reference to the Figure 3 , the side 20 is shown after the left and right folding flaps 232, 234 and 242, 244 have been folded around the left and right side edges 212, 214 and 222, 224 respectively. In this folded position, they are positioned substantially perpendicular to the central zone 210, respectively 220.

[0029] In reference to the Figure 4 , the blank 20 is shown after the additional folding of the assembly tabs 235 and 245 around the end edges 239 and 249 respectively and around the fold lines separating the first parts 235a and 245a from the second parts 235b and 245b. In this folded position, the second parts 235b, respectively 245b, are oriented substantially perpendicular to the left and right folding flaps 212, 214, respectively 222, 224.

[0030] In reference to the figure 5 , the blank 20 is shown after the additional folding of the lower and upper folding flaps 231, 233 and 241, 243 around the lower and upper longitudinal edges 211, 213 and 221, 223. In this pre-assembled configuration of the blank 20, corresponding to the final shape of the external shell 11 of the tray 10, the flaps 231, 233, respectively 241, 243, are positioned substantially perpendicular to the central zone 210, respectively 220, and to the left and right folding flaps 232, 234, respectively 242, 244, and are in contact with the second parts 235b, respectively 245b, of the assembly tabs 235, respectively 245. Furthermore, in this pre-assembled configuration of the blank 20, the through openings 18 are arranged opposite the adhesion zones 14 such that the adhesion zones 14 are completely visible through said through openings 18.

[0031] A comparison of the Figures 1 And5allows to see that the bottom wall 111 of the half-shell 11a, respectively 11b, corresponds substantially to the central zone 210, respectively 220, of the blank 20, and that the side wall 112 of the half-shell 11a, respectively 11b, is defined by the union of the folding flaps 231-234, respectively 241-244, arranged in their vertical position, between which are interposed the assembly tabs 235, respectively 245. The blank 20 having in principle, in its flat configuration, a uniform thickness over its entire surface, it must also be noted that this side wall 112 has a greater thickness at the level of the portions of the folding flaps 231-234, respectively 241-244, of the blank 20 which are superimposed with the second parts 235b, respectively 245b, of the assembly tabs 235, respectively 245.As a result, each of the adhesion zones 14 of the outer shell 11 is completely surrounded by one of said thicker portions of the side wall 112.

[0032] In the next manufacturing step, the outer shell 11 shown in the Figure 5 is arranged inside the thermoforming mold 1 shown in the Figure 6 . This mold 1 is formed of a lower die 2 and an upper die 3, said dies 2, 3 being movable relative to each other in the direction Z indicated on the Figure 6 so as to allow mutual approximation. The lower die 2 has a series of four hollow impressions 4 positioned according to a regular grid of two rows and two columns, each of the impressions 4 being intended to receive one of the half-shells 11a or 11b of two identical shells 11 arranged side by side. Each of the impressions 4 will advantageously have a shape complementary to those of the half-shells 11a and 11b so as to allow their accommodation without play inside the impressions 4. In particular, each of the impressions 4 comprises a series of four beveled surfaces 41 intended to support the first parts 235a and 245a of the assembly tabs 235 and 245 of the blank 20. In addition, punches 6 are arranged projecting relative to said beveled surfaces 41.These punches 6 are intended to locally deform the external face of the shells 11 when the shells 11 are placed inside the lower die 2 so that a temporary mechanical connection is made between said shells 11 and said lower die 2. These punches 6 therefore make it possible to hold the shells 11 inside the cavities 4 before closing the mold 1. This avoids in particular having to apply quick-setting glue to the surfaces of the blank 20 which overlap to hold the blank 20 in its pre-assembled configuration.

[0033] The upper die 3 has a series of four raised counterforms 5 preferably having a shape complementary to those of the impressions 4.

[0034] The dies 2, 3 are then heated to a temperature between 60°C and 130°C, and preferably between 80°C and 90°C. A plastic film 12 is then interposed between the lower die 2 and the upper die 3 before they are brought together until the mold 1 is closed. A vacuum suction may, if necessary, be applied inside the mold 1 so as to firmly press the plastic film 12 against the shells 11 and against the upper edge 7 of the lower die 2 which surrounds the cavities 4. This upper edge 7 comprises in particular a series of three hollow shapes 8 aligned along a median direction D of the lower die 2. Said hollow shapes 8 have a V-shaped profile and are configured to form the first V-shaped groove 16 and the second V-shaped groove 17 of the tray 10 shown in FIG. Figure 1 .

[0035] Once the film has been thermoformed, the mold 1 is opened and the tray 10 is removed. An additional operation of activating the adhesion zones 14 can then be carried out. Such a step is, for example, shown in the Figure 7 . It consists in particular of applying heat to the adhesion zones 14 through the inner casing 12 by means of electrodes 9 producing ultrasound. The heat applied by the electrodes 9 will depend on the activation temperature of the thermo-adhesive coating forming the adhesion zones 14. The adhesion zones 14 thus heated therefore make it possible to secure the inner casing 12 to the outer shell 11 by heat sealing. A subsequent separation of the two main components of the tray 10 may however be possible by applying a sufficiently large tearing force. This separation must generate a minimum quantity of material torn from the outer cardboard shell 11 so as to allow optimal recycling of the constituent materials of the tray 10.

[0036] Due to the particular positioning of the adhesion zones 14, namely in zones of the side wall 112 of each of the half-shells 11a and 11b which are surrounded by thicker portions of the side wall 112, said thicker portions corresponding, as described previously, to the portions of the folding flaps of the blank 20 which are superimposed with the assembly tabs of said blank 20, this joining also makes it possible to maintain the blank 20 in its pre-assembled configuration, given that the adhesion zones 14, when welded, prevent relative movement between said folding flaps and said assembly tabs.

[0037] The manufacturing steps described above therefore make it possible to form the tray 10 shown in the Figure 1 . These manufacturing steps, as well as the nature and shape of the constituent elements of the tray or the shape of the thermoforming mold implemented at this level, may however differ from those described above without departing from the scope of protection of the invention as claimed. In particular, it will be possible to use devices other than electrodes to heat-weld the internal envelope 12 to the external shell 11.

[0038] The method of the invention also makes it possible to form a 10' tray shown in the Figure 8 .

[0039] This tray 10' defines an interior storage space for a foodstuff. It comprises an outer shell 11, for example made of cardboard, and an inner envelope 12 formed of a plastic film internally covering the outer shell 11. The outer shell 11 comprises an octagonal-shaped bottom wall 111 and a side wall 112 completely surrounding the bottom wall 111 and which is substantially perpendicular thereto. The inner casing 12 is in at least partial contact with the side wall 112 and with the bottom wall 111. Preferably, the inner casing 12 will completely match the internal shape of the outer shell 11. The inner casing 12 is secured to the side wall 112 at a plurality of adhesion zones 14 arranged on an internal face of said side wall 112. These adhesion zones 14 have a circular shape and are made of a thermo-adhesive coating, which is activated under the effect of heat.The inner casing 12 comprises a peripheral edge 15 protruding from the outer shell 11 and arranged mainly in a plane parallel to the bottom wall 111.

[0040] In reference to the Figure 9 , there is shown a pre-cut and pre-folded 20' cardboard blank which is intended to form the external shell 11 of the 10' tray of the Figure 8 This blank 20' comprises a central zone 210 of octagonal shape delimited by a lower longitudinal edge 211, by an upper longitudinal edge 213, by a left lateral edge 212, and by a right lateral edge 214. The lower longitudinal edge 211, respectively upper 213, is connected respectively to the left 212 and right 214 lateral edges by two lower oblique edges left 215 and right 217, respectively by two upper oblique edges left 216 and right 218.

[0041] The central zone 210 is extended on each of its longitudinal and lateral edges by a folding flap, namely a lower folding flap 231, an upper folding flap 233, a left folding flap 232, and a right folding flap 234. The lower and upper longitudinal edges 211 and 213 and the left and right lateral edges 212 and 214 correspond to folding edges of the pre-folded blank 20' so as to allow the folding of the folding flaps 231-234 in a vertical position, perpendicular to the central zone 210. The lower and upper folding flaps 231, 233 are provided on their internal face with two circular zones 14 covered with a thermo-adhesive coating, each of said circular zones 14 being close to one of the end edges of said folding flaps 231, 233 which adjoins one of the oblique edges 215-218.Furthermore, the left and right folding flaps 232, 234 are extended on each of their end edges 239, which adjoin the oblique edges 215-218, by an assembly tab 235. Each of the assembly tabs 235 comprises a first part 235a of trapezoidal shape connected to one of the left or right folding flaps 232, 234 at one of the end edges 239 and a second part 235b connected to the first part 235a by a fold line. The end edges 239 correspond to folding edges of the pre-folded blank 20' so as to allow the assembly tabs 235 to be folded into a folded position in which they are oriented obliquely relative to the left and right folding flaps 232, 234. The second part 235b of the assembly tabs 235 is provided with a through opening 18, said through openings 18 having a circular shape substantially identical to that of the circular zones 14.

[0042] In reference to the figure 10 , the blank 20' is shown in its pre-assembled configuration corresponding to the final shape of the external shell 11 of the tray 10', the flaps 231, 233 being positioned substantially perpendicular to the central zone 210 and to the left and right folding flaps 232, 234 and being in contact with the second parts 235b of the assembly tabs 235. Furthermore, in this pre-assembled configuration of the blank 20', the through openings 18 are arranged opposite the adhesion zones 14 such that the adhesion zones 14 are completely visible through said through openings 18.

[0043] A comparison of the Figures 8 And 10allows to see that the bottom wall 111 of the external shell 11 corresponds substantially to the central zone 210 of the blank 20' and that the side wall 112 of the external shell 11 is defined by the union of the folding flaps 231-234 arranged in their vertical position, between which are interposed the assembly tabs 235. The blank 20' having in principle, in its flat configuration, a uniform thickness over its entire surface, it must also be noted that this side wall 112 has a greater thickness at the level of the portions of the folding flaps 231-234 of the blank 20' which are superimposed with the second parts 235b of the assembly tabs 235. As a result, each of the adhesion zones 14 of the external shell 11 is completely surrounded by one of said thicker portions of the side wall 112.

[0044] In the next manufacturing step, the outer shell 11 shown in the Figure 10 will be placed inside a thermoforming mold substantially similar to that shown in the Figure 6 This mold can thus be formed from a lower die 2 and an upper die 3, said lower 2 and upper 3 dies being movable relative to each other in the direction Z indicated on the Figure 6so as to allow mutual approximation. The lower die 2 will have at least one hollow impression configured to receive the outer shell 11. Said hollow impression will advantageously have a shape complementary to that of the outer shell 11 so as to allow it to be housed without play inside the impression. In particular, said hollow impression may comprise a series of four beveled surfaces intended to support the first parts 235a of the assembly tabs 235 of the blank 20'. In addition, punches may be arranged projecting relative to said beveled surfaces. These punches will be intended to locally deform the outer face of the outer shell 11 when it is placed inside the lower die so that a temporary mechanical connection is made between said outer shell 11 and said lower die 2.These punches will therefore make it possible to hold the outer shell 11 inside the hollow impressions before closing the thermoforming mold. This will in particular avoid having to apply quick-setting glue to the surfaces of the blank 20' which overlap to hold the blank 20' in its pre-assembled configuration.

[0045] The upper die 3 will have at least one raised counterform preferably having a shape complementary to that of the hollow impression of the lower die 2.

[0046] The following manufacturing steps will then be identical to those described previously for the formation of the tray 10.

Claims

1. A tray (10, 10'), notably for packaging a food product, comprising: - an outer shell (11) including at least one bottom wall (111) and at least one lateral wall (112), - an inner envelope (12) formed of a plastic film covering the inside of the outer shell (11), being in at least partial contact with said at least one lateral wall (112), the inner envelope (12) being secured to said at least one lateral wall (112) at a plurality of adhesion areas (14) disposed on an inner face of said at least one lateral wall (112), characterized in that each of the adhesion areas (14) is entirely surrounded by a thicker portion of said at least one lateral wall (112), and in that the outer shell (11) is formed from a precut blank (20, 20'), preferably made of cardboard, which is folded onto itself, said blank (20, 20') having assembly tabs (235, 245) provided with through openings (18) and foldable flaps (231, 233, 241, 243) intended to be folded over said assembly tabs (235, 245), the thicker portions of said at least one lateral wall (112) being formed by superimposed parts (235b, 245b) of the assembly tabs (235, 245) which are covered by said foldable flaps (231, 233, 241, 243) and parts of the foldable flaps (231, 233, 241, 243) which covers the assembly tabs (235, 245), the adhesion areas (14) corresponding to the portions of the foldable flaps (231, 233, 241, 243) which are disposed facing the through openings (18) of the assembly tabs (235, 245).

2. The tray (10, 10') according to claim 1, characterized in that the adhesion areas (14) have a circular shape.

3. The tray (10, 10') according to claim 1 or 2, characterized in that said at least one bottom wall (111) has an octagonal shape.

4. The tray (10, 10') according to any of the preceding claims, characterized in that the inner envelope (12) consists of a thermoplastic film which is secured to the outer shell (11) by heat welding.

5. The tray (10) according to any of the preceding claims, characterized in that the outer shell (11) is formed of two half-shells (11a, 11b) connected to each other by a hinge (13), each of the half-shells (11a, 11b) including a bottom wall (111) and a lateral wall (112).

6. The tray (10) according to claim 5, characterized in that the hinge (13) is formed by a fold line of the blank (20).

7. The tray (10) according to claim 5 or 6, characterized in that the two half-shells (11a, 11b) have identical shapes.

8. The tray (10) according to any of claims 5 to 7, characterized in that the bottom wall (111) of each of the half-shells (11a, 11b) has an octagonal shape.

9. The tray (10) according to any of claims 5 to 8, characterized in that the inner envelope (12) comprises a peripheral border (15) extending beyond the outer shell (11), said peripheral border (15) being provided with a first V-shaped groove (16) and a second V-shaped groove (17), said first and second grooves (16, 17) being disposed on either side of the hinge (13) of the outer shell (11) and together forming a hinge element for the inner envelope (12).

10. A method for manufacturing a tray (10, 10') according to any of the preceding claims, characterized by comprising the following steps of: - providing a precut blank (20, 20'), preferably made of cardboard, in a flat configuration, the blank comprising a central area (210) delimited at least by two longitudinal edges, namely a lower edge (211) and an upper edge (213), and by at least two lateral edges, namely a left edge (212) and a right edge (214), the central area (210) being extended along each of said longitudinal and lateral edges by a foldable flap (231-234), at least two (231, 233) of said foldable flaps being provided with areas (14), called adhesion areas, covered with a heat-adhesive coating, and at least two others (232, 234) of said foldable flaps being extended at each of their ends by an assembly tab (235) provided with a through opening (18); - providing a plastic film (12); - folding the blank (20, 20') onto itself into a preassembled configuration, in which the blank (20, 20') forms an outer shell (11) including at least one bottom wall (111) and at least one lateral wall (112), and in which the through openings (18) are positioned so as to be disposed opposite to the adhesion areas (14), the adhesion areas (14) being disposed on an inner face of said at least one lateral wall (112), each being entirely surrounded by two superimposed portions of the blank (20); - inserting the thus obtained outer shell (11) into a thermoforming mold (1); - inserting the plastic film (12) into the thermoforming mold (1); - closing the thermoforming mold (1); - heating and shaping the plastic film so as to form an inner envelope (12) covering the inside of the outer shell (11), being in at least partial contact with said at least one lateral wall (112) at the plurality of adhesion areas (14); - applying heat to the adhesion areas (14) so as to activate the heat-adhesive coating and thereby secure the inner envelope (12) to the outer shell (11) at said adhesion areas (14), the inner envelope (12) thus preventing the blank (20, 20') from returning to its flat configuration.

11. The method according to claim 10, characterized in that the blank (20) comprises two identical parts (21, 22) separated by a fold line (13), each of the parts (21, 22) being intended to form a half-shell (11a, 11b) of the outer shell (11) after folding the blank (20), the fold line (13) being intended to form a hinge connecting the two half-shells (11a, 11b) to each other.

12. The method according to claim 11, characterized in that each of the parts (21, 22) comprises a central area (210, 220) delimited at least by two longitudinal edges, namely a lower edge (211, 221) and an upper edge (213, 223), and by at least two lateral edges, namely a left edge (212, 222) and a right edge (214, 224), the central area (210, 220) being extended along each of said longitudinal and lateral edges by a foldable flap (231-234; 241-244), at least two (231, 233, 241, 243) of said foldable flaps being provided with adhesion areas (14), and at least two others (232, 234; 242, 244) of said foldable flaps being extended at each of their ends by an assembly tab (235, 245) provided with a through opening (18), said through openings (18) being positioned so as to be disposed opposite to the adhesion areas (14) in the preassembled configuration of the blank.

13. The method according to claim 11 or 12, characterized in that the central area (210, 220) has an octagonal shape.

14. The method according to any of claims 10 to 13, characterized in that the thermoforming mold (1) comprises retaining means (6) adapted to retain the outer shell (11) inside the mold (1) before closing the mold (1).

15. The method according to claim 14, characterized in that said retaining means comprise a plurality of punches (6) intended to locally deform an outer face of the outer shell (11).

16. The method according to any of claims 10 to 15, characterized in that the step of applying heat to the adhesion areas (14) is carried out by means of electrodes (9) producing ultrasounds.

17. The method according to any of claims 10 to 16, characterized in that the heat-adhesive coating consists of a PVA varnish.