Sports article made by means of an additive manufacturing process and method for manufacturing such an article

Abstract

The present invention relates to a sports article comprising an element (1) made by means of an additive manufacturing process, the element (1) comprising: - an external structure (10); - an internal structure (12) forming a three-dimensional lattice structure formed by repeating at least one elementary pattern; - an intermediate structure (14), the intermediate structure (14) joining the external structure (10) to the internal structure (12).

Description

[0001] Sports article produced using an additive manufacturing process and method of manufacturing such an article

[0002] The present application relates to a sporting article comprising at least one part produced by means of an additive manufacturing process. The present application also relates to an article of footwear, such as a sports shoe, comprising such a sole. A sporting article is, for example, a shoe sole (outer sole, including a midsole and / or a wear sole), body protection (knee pad, elbow pad, back protector, etc.), a helmet, a saddle, a child seat adaptable to a bicycle.

[0003] Additive manufacturing processes, such as 3D printing, have many advantages, including the ability to produce objects with varied and complex shapes, including shapes that are difficult or impossible to produce using conventional processes. When it is desired to produce, using an additive manufacturing process, an object with a particular mechanical behavior, and in particular a mechanical behavior requiring a high level of elasticity, it is known to produce at least part of such an object in the form of a three-dimensional lattice structure, or lattice structure. In such a structure, the combination of solid areas and empty areas, combined with the use of a material with suitable properties, makes it possible to obtain varied mechanical behaviors, without penalizing the mass of the whole.A lattice structure that must have uniform mechanical properties is generally produced by repeating an elementary pattern, this pattern being repeated according to the longitudinal, transverse and thickness dimensions of the object. However, the constraints leading to the design of a lattice structure may lead to the visual appearance of the outer surface thereof not being aesthetic, or in any case, not allowing sufficient freedom in the design of this outer surface, under penalty of altering the mechanical properties of the lattice structure. The present invention aims to provide an element produced by means of an additive manufacturing method, the element comprising a lattice structure conferring given mechanical properties, and an outer surface whose visual appearance is independent of the lattice structure.To this end, the invention relates to a sports article comprising an element produced using an additive manufacturing method, the element comprising:

[0004] - an external structure;

[0005] - an internal structure, forming a three-dimensional lattice structure formed by the repetition of at least one elementary pattern;

[0006] - an intermediate structure, the intermediate structure ensuring the junction between the external structure and the internal structure.

[0007] Thus, by providing an external structure forming the outer surface of the element, the external structure being connected to the internal structure by an intermediate structure, it is possible to make the design of the external structure and the design of the internal structure entirely independent. It thus becomes possible to maintain the mechanical and functional integrity of the internal structure, while defining the external structure according to the desired criteria, and in particular according to the desired visual appearance.

[0008] According to other characteristics of the invention, the sports article in accordance with the invention comprises one or more of the following optional characteristics, considered alone or in all possible combinations:

[0009] In one embodiment, the intermediate structure comprises connecting beams, each connecting beam connecting a node of an elementary pattern to the external structure.

[0010] In one embodiment, the external structure is formed at least in part by a three-dimensional lattice structure comprising beams connected by nodes, each connecting beam of the intermediate structure being connected either to a node of the external structure or to a solid portion of the external structure.

[0011] In one embodiment, for each connecting beam connected to a node of the external structure, the connecting beam is connected to this node according to a distance criterion between the node of the internal structure and the node of the external structure.

[0012] In one embodiment, the distance criterion is satisfied if the distance between the node of the internal structure and the node of the external structure is greater than a threshold value.

[0013] In one embodiment, the threshold value is strictly greater than the thickness of the connecting structure. In one embodiment, a connecting beam connected to a node of the internal structure is connected to the nearest node of the external structure.

[0014] In one embodiment, a connecting beam connected to a node of the internal structure is connected to a node located at a distance included in a predetermined range of distances, so as to satisfy at least one additional criterion, such as an angle between the connecting beam and the external structure at the connection.

[0015] In one embodiment, the thickness of the connecting structure is less than or equal to 40% of the smallest dimension of a parallelepiped, in particular a rectangular parallelepiped, in which the elementary pattern of the internal structure is inscribed, and preferably less than or equal to 25% of this dimension.

[0016] The invention also relates to a method of manufacturing a sports article as defined above, the method comprising the steps of:

[0017] - determine an external structure of the element;

[0018] - determine the internal structure inscribed in the internal volume delimited by the external structure, the internal structure being reduced in relation to this internal volume so as to respect at least one criterion relating to the truncation of at least part of the elementary patterns constituting the internal structure;

[0019] - determine an intermediate structure ensuring the junction between the internal structure and the external structure;

[0020] - producing the element using an additive manufacturing process. In one embodiment, the step of determining the intermediate structure comprises a sub-step of determining elementary pattern nodes to be connected to the intermediate structure.

[0021] In one embodiment, the intermediate structure comprises connecting beams, each connecting beam connecting a node of an elementary pattern to the external structure.

[0022] In one embodiment, the external structure is formed at least in part by a three-dimensional lattice structure comprising beams connected by nodes, each connecting beam of the intermediate structure being connected either to a node of the external structure or to a solid portion of the external structure.

[0023] In one embodiment, for each connecting beam connected to a node of the external structure, the connecting beam is connected to this node according to a distance criterion between the node of the internal structure and the node of the external structure.

[0024] In one embodiment, the distance criterion is satisfied if the distance between the node of the internal structure and the node of the external structure is greater than a threshold value.

[0025] In one embodiment, the threshold value is strictly greater than the thickness of the bonding structure.

[0026] In one embodiment, a connecting beam is connected to the nearest node.

[0027] In one embodiment, a connecting beam is connected to a node located at a distance included in a predetermined distance range, so as to satisfy at least one additional criterion, such as an angle between the connecting beam and the external structure at the connection.

[0028] In one embodiment, the criterion relating to the truncation of the elementary patterns is a criterion defining a maximum degree of truncation of the elementary patterns.

[0029] In one embodiment, the criterion is set so that no elementary pattern is truncated, or so that the maximum degree of truncation is less than or equal to 30%.

[0030] In one embodiment, the thickness of the connecting structure is less than or equal to 40% of the smallest dimension of a parallelepiped, in particular a rectangular parallelepiped, in which the elementary pattern of the internal structure is inscribed, and preferably less than or equal to 25% of this dimension.

[0031] Other characteristics and advantages of the present invention will appear on reading the description which follows and on examining the appended figures in which:

[0032] - figure 1 is a perspective view of an element produced using an additive manufacturing process in accordance with the invention;

[0033] - Figure 2 is a cross-sectional view of the element of Figure 1;

[0034] - figure 3 is a perspective view of the element of figure 2;

[0035] - figure 4 is a detail view of figure 1;

[0036] - Figure 5 is a schematic view of an elementary pattern of the vinyl type; - Figure 6 is a schematic view showing the internal structure of Figure 2 with a non-homogeneous repetition of the elementary pattern;

[0037] - Figure 7 is a perspective view of a sports shoe midsole produced in accordance with the invention;

[0038] - Figure 8 is a sectional view of the sole of Figure 8;

[0039] - Figure 9 is a view similar to Figure 4, the connection structure not being defined by any connection distance criterion value;

[0040] - figure 10 is a view similar to figure 9, the connection structure being defined by a first connection distance criterion value;

[0041] - Figure 11 is a view similar to Figure 9, the connection structure being defined by a second connection distance criterion value;

[0042] - Figure 12 is a diagram representing the steps of a manufacturing method in accordance with the invention.

[0043] Figures 1 to 4 illustrate an element 1 according to the invention, in the example a block produced by means of a manufacturing method according to the invention, and intended to constitute a sports article or to form a part of a sports article. The sports article may be, for example, a shoe sole (outer sole, including a midsole and / or a wear sole), body protection (knee pad, elbow pad, back protector, etc.), a helmet, a saddle, a child seat adaptable to a bicycle, etc.

[0044] Element 1 is in the example a block of generally cubic shape, which can for example serve as a constituent element of body protection such as a knee pad suitable for practicing a sport such as volleyball. Figure 1 shows element 1 in perspective. In this figure, only the external surface of element 1 is visible, consisting of an external structure 10, or external skin 10.

[0045] Figures 2 to 4 show element 1 of Figure 1 seen in section.

[0046] Figure 2 is a perspective view of element 1 in cross-section, that is to say in section in a plane parallel to the XY plane of Figure 1. Figure 3 is a partial view similar to Figure 2, element 1 being seen in perspective. Figure 4 is a detail view of Figure 2. As visible in Figures 2 to 4, element 1 comprises three interlinked structures:

[0047] - an external structure 10, or external skin 10;

[0048] - an internal structure 12, or functional structure 12; - an intermediate structure 14, or connecting structure 14, ensuring the junction between the external structure 10 and the functional structure 12.

[0049] The three structures 10, 12, 14 are obtained jointly by means of an additive manufacturing process. The boundary between the intermediate structure 14 and the internal structure 12 is shown in Figures 2 to 4 by the dotted line L. The boundary between the external structure 10 and the intermediate structure 14 is shown in Figure 4 by the dotted line M.

[0050] The internal structure 12 is formed by a three-dimensional lattice structure, that is to say a lattice-type structure. Thus, the internal structure 12 is formed by the repetition, along each of the longitudinal X, transverse Y and thickness Z directions of the element 1, of elementary patterns 120 which are described in more detail below. The structure of the elementary patterns 120, and the way in which they are repeated along the three directions X, Y, Z of the element 1 confer physical and mechanical properties to the internal structure 12, such as, for example, properties of resistance and elasticity, and, in particular, properties of damping and energy restitution in the event of deformation.

[0051] The outer skin 10, or outer structure, forms the outer surface of the element 1. The outer structure 10 is in the example formed by a three-dimensional lattice structure, formed partly by the repetition of elementary patterns, but not only. The outer structure 10 is the only structure of the element 1 which is entirely visible and is in particular intended to give the element 1 the desired visual appearance. Of course, when the outer structure 10 is formed at least partly by a three-dimensional lattice structure based on the repetition of an elementary pattern, the outer structure 10 remains different from the inner structure 12.

[0052] The intermediate structure 14, or connecting structure, ensures the junction between the external structure 10 and the internal structure 12. The intermediate structure 14 is in the example a three-dimensional lattice structure, comprising connecting beams 140. Providing an intermediate structure 14 makes it possible to ensure a junction between the internal structure 12 and the external structure 10, this junction respecting, on the one hand, the mechanical behavior specific to the internal structure 12, and, on the other hand, the desired visual appearance of the external structure 10. Providing such an intermediate structure 14 makes it possible in particular to avoid the alteration, or at least too significant an alteration, of the elementary patterns 120 which would be located at the interface between the internal structure 12 and the external structure 10 in the absence of an intermediate structure.Indeed, the absence of a connecting structure could require truncating a significant portion of many elementary patterns, and thus alter the overall mechanical behavior of the internal structure 12. The intermediate structure 14 also makes it possible to avoid excessively large aggregates of material which could harm the mechanical behavior of the internal structure 12. Preferably, the intermediate structure 14 will be as thin as possible. The thickness of the intermediate structure 14, which will depend in particular on the dimensions of the element 1 and also on the size of the elementary patterns of the internal structure 12, will preferably be less than 10 mm, or less than 6 mm.

[0053] In the example, at least a portion of the internal structure 12 is formed by the repetition of an elementary pattern 120 of vinyl type, this elementary pattern being shown in perspective in FIG. 5. The use of this elementary pattern makes it possible to give the internal structure 12 the desired properties of elasticity, deformability, damping and durability to give the element 1 the desired mechanical behavior. The internal structure 12 may however be formed by a lattice structure comprising other elementary patterns or comprising several types of elementary patterns. In particular, the internal structure 12 may comprise zones formed by the repetition of different patterns, with the aim of giving the element 1 damping properties, energy restitution and resistance which vary depending on the zone considered, or even depending on other criteria.Without limitation, the following basic patterns may be used: diamond pattern, octagonal edge pattern, octagonal vertex pattern, tetrahedral pattern, etc.

[0054] The mechanical characteristics of the lattice structure of the internal structure 12 can be adapted in particular by modifying parameters of the elementary pattern, among which are in particular the following parameters:

[0055] - size of the elementary pattern and number of repetitions on the axis considered (axes x, y, z visible in figure 1);

[0056] - the beam diameter, which is fixed mainly according to the desired rigidity for each beam: it is for example between 0.5 and 5 mm, or between 1 and 3 mm; - the size of the nodes, a node being defined as the intersection of at least two beams: the size of a node is for example between 100% and 130% of the diameter of the beams joining the node, or between 105% and 125%, or even between 110% and 120%;

[0057] - radius of curvature at the intersection between two or more beams: for example, it is between 1 and 5 mm, or between 2 and 3 mm. Preferably, the radius of curvature is such that it is equal to the beam diameter multiplied by a factor between 1 and 2, and for example equal to 1.5.

[0058] An elementary pattern 120 of the vinyl type is visible in Figure 5. It is an elementary three-dimensional structure, comprising a plurality of elementary structures 20 in the shape of a hexagon, each elementary structure 20 thus comprising six beams 22, some of these beams being common to at least two elementary structures. Nodes 24 connect two or more beams 22.

[0059] Like any elementary pattern, the vinyl-type elementary pattern can be modified by varying several parameters, such as the size and number of repetitions along each x, y and z axis, the beam diameter 22, the size of the nodes 24 or the radius of curvature at the intersection. The geometry based on hexagon shapes of this elementary pattern gives a lattice structure a high capacity for shock absorption as well as good energy restitution. The vinyl-type elementary pattern can therefore be particularly suitable for the production of sports shoe soles or absorption elements for personal protection such as knee pads.

[0060] In the example, the size of the elementary pattern 120 is 11 mm x 11 mm x 11 mm, which means that the elementary pattern 120 is repeated within the internal structure 12 every 11 mm in each direction x, y, z. In other words, the elementary pattern is inscribed in a rectangular parallelepiped whose dimensions are 11 mm x 11 mm x 11 mm.

[0061] Preferably, as shown in Figures 2 and 4, the thickness E of the connecting structure 14 is less than or equal to 10%, preferably 8%, of the total dimension D of the sports article measured in the same direction (direction A in Figure 4). For a sports shoe sole, the thickness of the connecting structure 14 is, for example, less than or equal to 5 mm. Cumulatively or alternatively, the thickness E of the connecting structure 14 is less than or equal to 50% of the smallest dimension of a rectangular parallelepiped in which the elementary pattern of the internal structure 12 is inscribed. For example, for an elementary pattern 120 whose dimensions are those given above, the thickness E is less than or equal to 5.5 mm. Preferably, the thickness E is less than or equal to 40%, or even 25% of the smallest dimension of the rectangular parallelepiped in which the elementary pattern of the internal structure 12 is inscribed.

[0062] Figure 6 shows an example of embodiment of the internal structure 12 of the element 1 in which the beam diameter of the elementary patterns 120 increases progressively along the arrow F. For the same type of elementary pattern, increasing the beam diameter will increase the resistance of the internal structure 12, but will in return reduce its elasticity.

[0063] Figures 7 and 8 show a midsole 2 of a sports shoe according to the invention. The sole 2 comprises an external structure 10 forming in particular the covering of the sole, and an internal structure 12, visible in Figure 8, which represents the sole 2 seen in section. As for the element 1 of Figures 1 to 4, the sole 2 comprises an intermediate structure 14 ensuring the junction between the internal structure 12 and the external structure 10.

[0064] A method according to the invention is described below, in particular in relation to Figure 12, for obtaining sports articles including elements as described above.

[0065] Such a method comprises a step 200 during which an external structure 10 of the element 1 is determined. This structure is determined as a function of the external volume of the element to be produced, and as a function of the type of structure desired: the external structure can be solid, or form a three-dimensional lattice structure, comprising both solid parts and lattice parts.

[0066] The method then comprises a step 202 during which the internal structure 12 inscribed in the internal volume delimited by the external structure is determined, the internal structure being reduced relative to this internal volume so as to respect at least one criterion representative of the integrity of at least a portion of the elementary patterns constituting the internal structure. This criterion may be, for example, a degree of truncation (average or maximum) permitted for all the elementary patterns of the internal structure. For example, it may be necessary through this criterion to impose that no elementary pattern be truncated. Alternatively, it may be necessary, for example, to impose that no elementary pattern be truncated beyond a given degree of truncation. The degree of truncation may be, for example, expressed by a percentage giving the truncated volume relative to the initial volume of the elementary pattern.This value will be, for example, 30%, meaning that each elementary pattern will retain a volume after truncation greater than or equal to 70% of its initial volume.

[0067] The method then comprises a step 204 during which an intermediate structure 14 is determined, ensuring the junction between the internal structure and the external structure. This step makes it possible to determine the set of connecting beams 140 which will connect an elementary pattern of the internal structure to the external structure. Preferably, each connecting beam 140 will be connected to a node of an elementary pattern 120. The method will thus comprise a sub-step aimed at determining the set of nodes of elementary patterns to be connected to the connecting structure. The elementary patterns concerned are the elementary patterns forming the external surface of the internal structure 12. Among these elementary patterns, it is determined which nodes must be attached to the external structure, and therefore be connected to the intermediate structure.To discriminate these nodes, the following rule can be applied, for example: any node which is the intersection of fewer than three beams of the elementary pattern must be connected to the intermediate structure and therefore to a connecting beam 140. Thus, each node which must be connected to the external structure 10 will be connected to a connecting beam 140.

[0068] Each connecting beam 140 will further be connected to the external structure 10. If, near a connecting beam 140, the external structure 10 comprises a lattice part, therefore comprising beams 100 connected by nodes 102, the connecting beam 140 will be connected to a node 102. Thus, each connecting beam 140 will be connected either to a node or to a solid part of the external structure 10.

[0069] The definition of each connecting beam may obey one or more criteria. Among these criteria, a first distance criterion will be applied, that is to say that the choice of the connection location between a connecting beam 140 and the external skin 10 will be a function of the distance to the connection location between this connecting beam 140 and the internal structure. For example, it may be required that this distance be as short as possible. Or it may be required that it be the shortest possible distance by taking into account one or more additional criteria, such as for example the angle between the connecting beam and the external structure at the connection. It may also be possible to take into account size criteria (diameter, length, etc.) and shape criteria (for example that the connecting beam has a particular shape, such as a helical shape).

[0070] Figures 9 to 11 are views similar to Figure 4 showing the influence of the above-mentioned distance criterion, or connection distance criterion.

[0071] The value of the thickness E of the connecting structure 14 being fixed, the distance criterion will influence the length of the connecting beams 140, and, consequently, the angle formed by these connecting beams 140 and the direction normal to the direction tangent to the external structure 10 at the location of the connection of a given connecting beam 140 (in the example of figures 9 to 11, the external structure 10 being rectilinear, the normal direction is constant and corresponds to the direction of the axis A). In the example of figures 9 to 11, the value of the thickness E is fixed at approximately 5 mm.

[0072] In the example of Figure 9, no distance criterion has been imposed, and it is observed that each connecting beam 140 is connected to the nearest node of the internal structure 12. This configuration implies, as visible in Figure 9, that each connecting beam 140 extends in the direction normal to the tangent to the external structure 10, and therefore, in the example, in a direction parallel to the axis A.

[0073] In the example of Figure 10, a distance criterion is imposed, and, more precisely, a distance strictly greater than a threshold value equal to 10 mm is imposed. This implies that each connecting beam 140 must be connected to a node of the internal structure 12 located more than 10 mm from its connection point with the external structure 10. In other words, each connecting beam must have a length strictly greater than 10 mm. This constraint implies that the connecting beams can no longer be connected to the nearest node of the internal structure 12. As can be seen, this constraint has an influence on the angle formed between each connecting beam and the direction normal to the tangent to the external structure 10, which is then necessarily non-zero. Thus, each connecting beam 140 is inclined with respect to the direction normal to the tangent to the external structure 10, and therefore with respect to the axis A.

[0074] In the example of Figure 11, a distance criterion similar to that of Figure 10 is imposed, but the threshold value is here equal to 15 mm. This results in an angle between each connecting beam 140 and the direction normal to the tangent to the external structure 10 greater than that induced in the case of Figure 10. In other words, the connecting beams 140 are more strongly inclined relative to the axis A in the case of Figure 11. Imposing a distance criterion as illustrated in Figures 10 and 11 makes it possible to improve the mechanical behavior of the connecting structure 14, in particular when qualities of flexibility and cushioning are required, for example in the case of a shoe sole.

[0075] At the end of this stage, the intermediate structure is determined in such a way as to ensure the role of junction between the internal and external structures, in order to best respect the functional integrity of the internal structure and thus optimize the mechanical behavior of the entire element 1 obtained.

[0076] The method then comprises the step 206 of producing the element 1, comprising the three structures determined as described above, by means of an additive manufacturing method. The element 1 may form the sports article as such, or form only a part thereof, in which case a step of assembling the element 1, for example to a support or to another element of the sports article, may be required.

[0077] Additional steps can be implemented after additive manufacturing. For example, a sandblasting step cleans and smooths the surface of the resulting component, which can be useful for improving the component's aesthetics and performance. A chemical smoothing step can also be implemented after additive manufacturing. This step improves the component's durability, as well as its aesthetic appearance.

[0078] The method may be implemented with any type of suitable material, including thermoplastic materials, for example polymer materials such as polyurethane, polyethylene, polypropylene, polystyrene, polycarbonate, acrylonitrile butadiene styrene, polyamide, polyethylene terephthalate, thermoplastic copolyamide, ether-amide block copolymer, etc.

[0079] The method according to the invention is suitable for the production of sports articles which may include elements produced by additive manufacturing, such as for example: shoe soles (outer soles, including a midsole and / or a wear sole), body protection (knee pads, elbow pads, back protectors, etc.), helmets, bicycle saddles, a child seat adaptable to a bicycle, etc.

Claims

CLAIMS 1. Sports article comprising an element (1) produced using an additive manufacturing process, the element (1) comprising: - an external structure (10); - an internal structure (12), forming a three-dimensional lattice structure formed by the repetition of at least one elementary pattern (120); - an intermediate structure (14), the intermediate structure (14) providing the junction between the external structure (10) and the internal structure (12).

2. Sports article according to the preceding claim, in which the intermediate structure (14) comprises connecting beams (140), each connecting beam (140) connecting a node (24) of an elementary pattern (120) to the external structure (10).

3. Sports article according to the preceding claim, in which the external structure (10) is formed at least in part by a three-dimensional lattice structure comprising beams (100) connected by nodes (102), each connecting beam (140) of the intermediate structure (14) being connected either to a node (102) of the external structure (10), or to a solid part of the external structure (10).

4. Sports article according to the preceding claim, in which, for each connecting beam (140) connected to a node (102) of the external structure (10), the connecting beam (140) is connected to this node (102) according to a distance criterion between the node (120) of the internal structure (12) and the node (102) of the external structure (10).

5. Sports article according to the preceding claim, in which the distance criterion is satisfied if the distance between the node (24) of the internal structure (12) and the node (102) of the external structure (10) is greater than a threshold value.

6. Method according to the preceding claim, in which the threshold value is strictly greater than the thickness of the connecting structure (14).

7. A sporting article according to claim 4, wherein a connecting beam (140) connected to a node (24) of the internal structure (12) is connected to the nearest node (102) of the external structure (10).

8. A sporting article according to claim 4, wherein a connecting beam (140) connected to a node (24) of the internal structure (12) is connected to a node (102) located at a distance included in a predetermined range of distances, so as to respect at least one additional criterion, such as an angle between the connecting beam (140) and the external structure (10) at the connection.

9. Sports article according to one of the preceding claims, in which the thickness (E) of the connecting structure (14) is less than or equal to 40% of the smallest dimension of a parallelepiped, in particular a rectangular parallelepiped, in which the elementary pattern (120) of the internal structure (12) is inscribed, and preferably less than or equal to 25% of this dimension.

10. Method for manufacturing a sports article comprising an element (1) intended to be produced by means of an additive manufacturing method according to one of the preceding claims, the method comprising the steps of: - determining (200) an external structure (10) of the element (1); - determining (202) the internal structure (12) inscribed in the internal volume delimited by the external structure, the internal structure being reduced in relation to this internal volume so as to respect at least one criterion relating to the truncation of at least part of the elementary patterns constituting the internal structure (12); - determining (204) an intermediate structure (14) ensuring the junction between the internal structure and the external structure; - producing (206) the element (1) using an additive manufacturing process.

11. Method according to the preceding claim, in which the step of determining (204) the intermediate structure (14) comprises a sub-step of determining nodes (24) of elementary patterns (120) to be connected to the intermediate structure (14).

12. Method according to the preceding claim, in which the intermediate structure (14) comprises connecting beams (140), each beam link (140) connecting a node (24) of an elementary motif (120) to the external structure (10).

13. Method according to the preceding claim, in which the external structure (10) is formed at least in part by a three-dimensional lattice structure comprising beams (100) connected by nodes (102), each connecting beam (140) of the intermediate structure (14) being connected either to a node (102) of the external structure (10), or to a solid part of the external structure (10).

14. Method according to the preceding claim, in which, for each connecting beam (140) connected to a node (102) of the external structure (10), the connecting beam (140) is connected to this node (102) according to a distance criterion between the node (24) of the internal structure (12) and the node (102) of the external structure (10).

15. Method according to the preceding claim, in which the distance criterion is satisfied if the distance between the node (24) of the internal structure (12) and the node (102) of the external structure (10) is greater than a threshold value.

16. Method according to the preceding claim, in which the threshold value is strictly greater than the thickness of the connecting structure (14).

17. The method of claim 13, wherein the connecting beam (140) is connected to the nearest node (102).

18. The method of claim 13, wherein the connecting beam (140) is connected to a node (102) located at a distance included in a predetermined distance range, so as to respect at least one additional criterion, such as an angle between the connecting beam (140) and the external structure (10) at the connection.

19. Method according to one of claims 10 to 18, in which the criterion relating to the truncation of the elementary patterns is a criterion defining a maximum degree of truncation of the elementary patterns.

20. Method according to the preceding claim, in which the criterion is set so that no elementary pattern is truncated, or so that the maximum degree of truncation is less than or equal to 30%.

21. Method according to one of the preceding claims, in which the thickness (E) of the connecting structure (14) is less than or equal to 40% of the smallest dimension of a parallelepiped, in particular a rectangular parallelepiped, in which the elementary pattern (120) of the internal structure (12) is inscribed, and preferably less than or equal to 25% of this dimension.

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