ARCHITECTURAL GRID STRUCTURE FOR A DEVICE WITH A FLEXIBLE INTERFACE

Description

Domaine technique

[0001] The present invention relates to the field of lattice-structured designs, particularly for forming a device with a flexible interface, for example, a padded one. These lattice-structured designs can be intended to absorb shock and / or provide body support, such as a seat cushion, a cushion, a mattress, an armrest, a headrest, a wrist rest, a grip, or helmet padding. Etat de la technique antérieure

[0002] Structures with a lattice architecture exhibit significant open porosity. They are formed of strands or beams, generally dense, connected to each other according to elementary geometric patterns that repeat periodically in space. They can possess advantageous compressive mechanical properties, notably the ability to withstand large deformations without failure or irreversible deformation. They are thus well-suited to applications where the capacity to store and / or dissipate energy under compression is important, for example, in the design of shock absorbers. They are also suitable for applications where user comfort is desired, for example, in the design of body support components such as seat cushions, cushions, mattresses, armrests, headrests, wrist rests, or gripping elements such as handles.

[0003] In these applications, structures with a low elastic stiffness modulus and / or the ability to absorb and / or dissipate a high amount of deformation energy before rupture, also known as densification per unit volume, are particularly sought.

[0004] The compressive mechanical properties of a lattice-structured architecture depend on the constituent source material and differ according to the elementary geometric pattern formed by the strands / beams, as well as its dimensional parameters. The article by M. Nasim and U. Galvanetto, "Mechanical characterisation of additively manufactured PA12 lattice structures under quasi-static compression," Materials Today Communications, Volume 29, 2021, 102902, compares the mechanical properties of lattice-structured materials as a function of the elementary pattern of the strands / beams.

[0005] Among various known elementary patterns, the rhombic dodecahedral pattern exhibits a low elastic stiffness modulus and a high densification per unit volume.

[0006] We illustrated to figures 1A et 1B a lattice 1 formed of a plurality of elementary motifs of rhombic dodecahedral type 2 repeated periodically and in contact with each other and at figures 2A, 2B et 2C An elementary motif of the rhombic dodecahedron type 2. The elementary motif 2 comprises twenty-four strands 3 linked together to form the edges of a rhombic dodecahedron 4. The rhombic dodecahedron 4 comprises six acute-angled vertices 5 and eight obtuse-angled vertices 6. An acute-angled vertex 5 is a vertex where four faces of the rhombic dodecahedron 4 meet at their acute angles. An obtuse-angled vertex 6 is a vertex where three faces of the rhombic dodecahedron 4 meet at their obtuse angles. The elementary motif 2 is inscribed in an elementary cell 8, which corresponds to the rectangular parallelepiped circumscribed by each of the acute-angled vertices 5. The elementary motif 2 also includes eight connecting strands 7, each linking one of the obtuse-angled vertices 6 to the vertex nearest to the elementary cell 8. The connecting strands 7 extend along the diagonals of the elementary cell 8.

[0007] The elementary motif of the rhombic dodecahedral type 2 is similar to the motif called "fluorite" in the software "nTopology 3.26.3" developed and marketed by the company nTopology, INC. Indeed, it is similar to a crystal structure of fluorite for which each of the atomic sites would have been linked together by strands.

[0008] As illustrated in figures 1A et 1B , the adjacent rhombic dodecahedral 2 type elementary motifs are fixed together by contact between their respective bonding strands 7 and by contact between their respective acute-angled vertices.

[0009] Although a lattice-structured architecture 1 based on a periodic elementary motif 2 of the rhombic dodecahedral type exhibits good mechanical properties, particularly for replacing certain polyurethane foams, it nevertheless has a small contact area 9. The contact area 9 is the set of points of the structure 1 on the surface enveloping an outer face 22 of said structure 1. For the monolithic lattice-structured architecture 1 of the figures 1A et 1B The contact surface 9 is defined by the ends 7a of the connecting strands 7 and the acute-angled vertices 5 on the outer face 22 of the structure 1. Thus, when a solid, for example a part of a human body, is brought into contact with the structure 1, the contact force is distributed over a small contact area. This results in locally high stresses at the contact surface 9. Consequently, when the body is supported, the user experiences a sensation of discomfort, as the free strands and edges then act like a set of sharp points.

[0010] US 2021 / 187897 A1 describes a micro-network structure comprising a plurality of interconnected filaments extending in at least three different directions from several nodes.

[0011] EP 3 954 252 A1 relates to a passenger seat cushion element and a filler body.

[0012] Therefore, there is a need for a lattice-structured architecture that overcomes these drawbacks. Furthermore, there is a need for a lattice-structured architecture with a low modulus of elastic stiffness and high density per unit volume, the structure presenting a large contact area when the body is supported and, preferably, being pleasant to the touch. Exposé de l'invention

[0013] The invention relates to an architecturally structured lattice structure comprising: a body lattice comprising a plurality of periodically repeated elementary body motifs in contact with each other, each elementary body motif comprising body strands connected to each other to form the edges of a polyhedron and connecting strands linking the polyhedron to the vertices of the elementary body cell, which is the smallest rectangular parallelepiped circumscribed about the elementary body motif, a surface lattice defining a face of the structure and at least partially covering the body lattice, the surface lattice comprising a plurality of periodically repeated surface elementary motifs, each surface elementary motif comprising a support block extending in a median plane parallel to the face of the structure defined by the surface lattice, and deformable feet, each having one end fixed to the support block and distant from the other feet, and another end,distant from the median plane and common to all other feet and to at least one strand of the body, the surface lattice being configured so that under the effect of a normal compressive force In the median plane, the feet deform to move the support block in translation along an axis parallel to the compression force.

[0014] An "elementary cell" is the smallest rectangular parallelepiped circumscribed by an elementary motif. The elementary cell is a fictitious geometric construction, that is to say, it is not made of matter unlike strands and beams.

[0015] Advantageously, the surface lattice increases the contact area of ​​the lattice structure without significantly affecting its compressive mechanical properties, which are primarily determined by the body lattice. The contact area is formed by the support block and can therefore be free of sharp points. As a result, the contact stress is lower during body support, and the component is thus more comfortable for the user.

[0016] Furthermore, a compressive force applied to the surface truss is transmitted homogeneously to the body truss. This results in a good distribution of stresses throughout the entire truss structure and therefore improved user comfort.

[0017] Preferably, the feet of each surface element are separated from one another along the portions between the end fixed to the support block and the end common to each foot and at least one body strand. Advantageously, the surface lattice is then more flexible, that is, it has a lower modulus of elastic stiffness, and, under a compressive force applied to the surface lattice, the body lattice is only slightly constrained by the surface lattice. Preferably, each foot is formed from a single branch.

[0018] Preferably, the end common to each of the feet and to at least one body strand is fixed to one of the vertices of the polyhedron. Preferably, said vertex lies within one of the faces of the elementary body cell. Preferably, said vertex is at the center of said face of the elementary body cell.

[0019] Preferably, for each of the feet, the distance, measured parallel to the median plane, between the end fixed to the support block and the other end common to each of the feet and to at least one body strand is between 2 and 50 mm.

[0020] Preferably, viewed orthogonally to the median plane, the end common to each of the feet and to at least one body strand is equidistant from each of the ends fixed to the support block of the surface element. Advantageously, this improves the distribution of the compressive force at each of the feet.

[0021] Preferably, viewed orthogonally to the median plane, each end fixed to the support block is equidistant from the two nearest other ends fixed to the support block. Advantageously, this improves the distribution of the compressive force at each foot.

[0022] Preferably, each superficial elementary motif has four feet. Preferably, viewed orthogonally to the median plane, the feet together form an X-shaped motif.

[0023] Preferably, each foot is symmetrical to at least two adjacent feet, each symmetry being performed with respect to a plane perpendicular to the median plane.

[0024] Each foot can extend along a straight line, including a rectilinear one. The straight line can form an angle between 10° and 70° with the median plane.

[0025] According to a preferred variant, each of the feet can extend along a curved line, preferably the curved line being a Bézier curve or an arc of an ellipse. Preferably, the curved line is a quadratic or cubic Bézier curve.

[0026] A Bézier curve is a curve defined by the following equation: B t = ∑ i = 0 n n i 1 − t n − i t i P i ,

[0027] In which, t is a positive real number between 0 and 1, n is the degree of order of the Bézier curve, greater than or equal to two, and the P i are the control points of the Bézier curve with P 0 the initial control point of the quadratic Bézier curve located at the common end to each of the feet and at least one body strand, and, P n the final control point of the quadratic Bézier curve located at the end fixed to the support block.

[0028] A quadratic Bézier curve, respectively cubic, is a Bézier curve of order n equal to two, respectively to 3.

[0029] The curved line can be drawn by computer-aided design software or by means of algorithmic design software such as the "Grasshopper ®< software by Robert McNeel & Associates, and in particular its "Bezier Span" function.

[0030] The curved line can be contained within a plane inclined to the median plane at an angle of inclination between 5° and 90°. In particular, the control points P i of the Bézier curve can be included in said inclined plane.

[0031] The angle of inclination can be 90°. If so, viewed orthogonally to the median plane, each leg extends in a straight line. Such an arrangement of the legs advantageously prevents any rotation of the support block about an axis lying in the median plane. Preferably, viewed orthogonally to the median plane, each leg forms an angle of 2π / N with the adjacent legs, where N is the number of legs. Preferably, the legs are invariant under at least one rotation about a reinforcement axis normal to the median plane, preferably a rotation of angle 2π / N, where N is the number of legs. In particular, N can be four, with the rotation of invariance being 90°.

[0032] Alternatively, the angle of inclination can be less than 90°. Viewed orthogonally to the median plane, each foot can extend to form an elliptical arc, preferably a circular arc. Preferably, viewed orthogonally to the median plane, the feet form an X made up of two back-to-back Cs. In other words, viewed orthogonally to the median plane, the feet can form a cursive X.

[0033] Alternatively, the curved line can be three-dimensional. A three-dimensional curve is a curve that cannot be entirely contained within a plane. In particular, the degree of order n of the Bézier curve can be greater than or equal to three, and the control points Pi of the Bézier curve are arranged in such a way that they cannot be contained together in the same plane.

[0034] Preferably, the curved line is free of inflection points. An "inflection point" is a point where the curve changes its sign of curvature, that is, the curve changes from concave to convex or vice versa.

[0035] Preferably, the curved line is concave when viewed from the support block.

[0036] Preferably, the tangent of the curved line at the end fixed to the support block forms an angle between 45° and 135° with the median plane, preferably equal to 90°. In the case of a Bézier curve, said tangent is collinear with the vector PnPn-1 defined by the final control point Pn of the Bézier curve and the penultimate control point Pn-1 of the Bézier curve.

[0037] Preferably, the tangent of the curved line at the common end of each foot and at least one body strand is parallel to the median plane. In the case of a Bézier curve, said tangent is collinear with the vector P0P1 defined by the initial control point P0 of the Bézier curve and the second control point P1 of the Bézier curve.

[0038] Preferably, the feet are invariant under at least one rotation around an axis of reinforcement normal to the median plane, preferably by a rotation of angle π.

[0039] Preferably, the distance, measured orthogonally to the median plane, between the end fixed to the support block and the end common to each of the feet and to at least one body strand is between 3 and 50 mm.

[0040] Preferably, viewed orthogonally to the median plane, the shortest distance between each foot of the surface element and the nearest foot of the nearest adjacent surface element is greater than 1 mm. Advantageously, this limits, or even eliminates, the risk of collision between the feet of two adjacent surface elements when a compressive force is applied to said surface elements.

[0041] Preferably, each surface element is inscribed within a surface element cell of rectangular parallelepiped shape and having one face contained within a face of one of the body element cells. Preferably, said faces are concentric.

[0042] Preferably, said face of the superficial elementary cell has sides between 5 mm and 50 mm.

[0043] Preferably, said face of the superficial elementary cell is square.

[0044] Preferably, the support block comprises reinforcement consisting of a plurality of interconnected reinforcing beams forming the sides of at least one polygon parallel to the median plane. Advantageously, the reinforcement uniformly transmits the compressive force to each of the legs. This uniform transmission ensures that the support block remains parallel to the median plane during deformation of the legs.

[0045] Preferably, the end of each leg attached to the support block is fixed to the frame. This simplifies the attachment of each leg to the support block, preventing any collision between the leg and the support block during leg deformation.

[0046] The support block can consist of the reinforcement.

[0047] Preferably, the reinforcement has a thickness, measured orthogonally to the median plane, of between 0.6 and 5 mm, preferably between 0.8 and 3 mm.

[0048] Preferably, the reinforcing beams are made of a polymer material or a metal or a composite, for example a thermoplastic, preferably a thermoplastic elastomer, or a polymer filled, for example, with glass microbeads.

[0049] Preferably, the reinforcement comprises at least four, preferably at least six, reinforcing beams.

[0050] The polygon can be a hexagon, preferably convex and / or irregular.

[0051] The reinforcing beams can be connected to form the sides of two polygons parallel to the median plane, one of the polygons, called the inner polygon, being arranged within the other polygon, called the outer polygon. Preferably, the reinforcement includes connecting beams, each connected at one end to the reinforcing beams of the inner polygon and at the other end to the reinforcing beams of the outer polygon. Preferably, the inner polygon is a scaled-down version of the outer polygon. Preferably, each polygon is a rectangle, preferably a square. Preferably, the end of each leg attached to the support block is attached to the reinforcing beams of the outer polygon.

[0052] Preferably, the reinforcement extends in a plane parallel to the median plane.

[0053] Preferably, the reinforcement is invariant under at least one rotation about a reinforcement axis normal to the median plane, preferably by a rotation of angle π / 2. Preferably, the reinforcement axis passes through the common end of each of the feet and at least one body strand.

[0054] Preferably, the reinforcement is shaped to be distant from the body and connecting strands when the feet are deformed by compressive stress and the ends attached to the support block are contained within the elementary body cell. Advantageously, the absence of contact between the reinforcement and the body and connecting strands when the feet are deformed in compression reduces the influence of the surface truss on the mechanical properties of the truss-structured architecture, particularly on its density per unit volume. In particular, the mechanical behavior of the surface truss under a compressive stress normal to the median plane is primarily determined by the deformation of the feet.

[0055] Preferably, the reinforcement is shaped to be superimposed at the connection points between the bonding strands and the body strands when the feet are deformed by the compressive force.

[0056] Preferably, the support block covers at least 50% of the face of the superficial elementary motif viewed orthogonally to the median plane.

[0057] Preferably, the support block includes a skin extending parallel to the median plane and covering at least 50% of the face of the surface element when viewed orthogonally to the median plane. Advantageously, the skin increases the contact area of ​​the lattice structure. The skin also prevents contact between the user supporting themselves on the lattice structure and the tips of the polyhedra of the body elements. Furthermore, the skin can enhance the aesthetic appearance of the lattice structure. In particular, the skin can include a visual marker, such as a print, imprint, and / or texture. The skins of several support blocks, especially adjacent ones, can define a visual motif, such as a logo. Additionally, the skin can cover the feet of the surface lattice.It thus protects the feet of the surface trellis by preventing the feet from being pulled out or by preventing unwanted mechanical stress on said feet.

[0058] The support block can consist of the skin. The feet are then fixed directly to the skin. The thickness of the skin can be adapted accordingly. In particular, the skin can be thicker at the points where the feet are fixed to it.

[0059] Preferably, the skin has a thickness of between 0.6 and 2 mm, preferably between 0.8 and 1.5 mm.

[0060] Preferably, the skin is made of a polymer material or a metal or a composite, for example a thermoplastic, preferably a thermoplastic elastomer, or a polymer filled, for example, with glass microbeads.

[0061] Preferably, the skin is supported by the frame, preferably fixed to the frame.

[0062] The skin can be superimposed on the framework. Preferably, viewed orthogonally to the median plane, the skin protrudes beyond the framework.

[0063] Alternatively, the skin can be coplanar with the reinforcement. Preferably, the skin is housed within at least one of the polygons, preferably the inner polygon, formed by the reinforcement beams.

[0064] The surface layer of the elementary motif can be separated from the layers of other elementary motifs. The surface lattice then transmits the compressive force to the body lattice in a localized manner. The surface elementary motifs subjected to the compressive force transmit it to adjacent elementary motifs within the body. The influence of the surface elementary motifs not subjected to the compressive force on the mechanical behavior of the lattice structure is negligible.

[0065] Alternatively, the skin of the surface element includes contact points that securely connect it to the skins of adjacent surface elements. This results in a more homogeneous transmission of the compressive force from the surface truss to the body truss across the entire structure. The skin is also more robust. The interconnectedness of the skins of the various surface elements limits the risk of individual detachment of a surface element and prevents any rotational movement of each support block.

[0066] Preferably, the skin is shaped to be distant from the bonding strands when the feet are deformed by the compressive force and the ends fixed to the support block are included in the elementary body cell.

[0067] Preferably, the skin has an opening aligned orthogonally to a vertex of the polyhedron, perpendicular to the median plane. Preferably, the opening is aligned orthogonally to the median plane with the common end of each of the feet and at least one body strand. The opening facilitates the removal of powder from the structure according to the invention after its fabrication by a powder bed additive manufacturing process. Furthermore, thanks to the opening, the skin does not press against a point during the transmission of the compressive force, thus limiting the risk of skin tearing.

[0068] Preferably, the lattice-structured architecture is monolithic. Preferably, the lattice-structured architecture is made of a single material.

[0069] Preferably, the thickness of the surface mesh, measured orthogonally to the median plane, is between 4 and 50 mm, preferably between 4 and 20 mm.

[0070] Preferably, the elementary cell of the body is cubic, preferably with sides between 5 and 50 mm.

[0071] Preferably, the elementary cell of the body is circumscribed around the polyhedron.

[0072] Preferably, the polyhedron is a rhombic dodecahedron. Preferably, the connecting strands link the obtuse-angled vertices of the rhombic dodecahedron to the vertices of the elementary body cell.

[0073] A "rhombic dodecahedron" is a convex polyhedron with twelve rhombic faces. It therefore includes six vertices with acute angles, eight vertices with obtuse angles and twenty-four edges.

[0074] Preferably, the diameter of the body strands and / or the diameter of the connecting strands and / or the diameter of the feet is between 0.6 and 3 mm, preferably between 0.8 and 2 mm.

[0075] Preferably, the body strands and / or the linking strands and / or the feet are made of a polymer material or a metal or a composite, for example a thermoplastic, preferably a thermoplastic elastomer, or a polymer filled, for example, with glass microbeads.

[0076] The invention also relates to a device comprising a lattice-structured architecture according to the invention, the device being selected from: a shock absorber, a body support, for example a seat cushion, a cushion, a mattress, an armrest, a headrest, helmet padding, or a wrist rest, and a grasping device, for example a gripping handle, or a steering wheel.

[0077] The invention also relates to a method for manufacturing an architecturally structured lattice structure according to the invention using an additive manufacturing technique. Brève description des dessins

[0078] Other advantages and features will become clearer upon reading the detailed description, provided for illustrative purposes only and not as a limitation, with reference to the following figures: [ Fig 1A] et [Fig 1B ] are perspective and top views respectively of a lattice comprising a plurality of periodic elementary motifs of rhombic dodecahedral type; [ Fig 2A], [Fig 2B] et [Fig 2C ] are perspective, top, and front views respectively of an elementary rhombic dodecahedral pattern; [ Fig 3A] et [Fig 3B ] are perspective and top views respectively of a lattice-structured architectural framework according to the invention, the bases of the superficial elementary motifs extending along curved lines each contained in a plane perpendicular to the median plane of the support block; [ Fig 3C ] is a front view of part of the lattice-structured architecture of figures 3A et 3B ; Fig 4A ], [ Fig 4B] et [Fig 4C ] are perspective, bottom and front views respectively of a superficial elementary motif of the lattice-like architectural structure of figures 3A et 3B ; Fig 5], [Fig 6 ] And [ Fig 7 ] are perspective views of examples of lattice-structured architectural designs according to the invention, showing different positions of the intermediate control points of the quadratic Bézier curves followed by each of the legs; [ Fig 8 ] is a top view of part of the lattice-structured architecture of figures 3A, 3B And 3C , the skins of the support blocks are not shown; [ Fig 9A ] is a perspective view of a lattice-structured architectural design according to the invention, the feet of the superficial elementary motifs extending along curved lines, each contained in a plane oblique to the median plane of the support block, the skins being joined to each other; [ Fig 9B ] is a front view of part of the lattice-structured architecture of the figure 9A ; Fig 10 ] is a top view of the lattice-structured architectural framework of figures 9A et 9B , the skins of the support blocks are not shown; [ Fig 11 ] is a perspective view of a portion of a lattice-structured architectural element according to the invention, the feet of the surface elementary motifs extending along a curved line being a cubic and three-dimensional Bézier curve; [ Fig 12A] et [Fig 12B ] are perspective and top views respectively of a lattice-structured architectural framework according to the invention, the reinforcement of each of the surface motifs being coplanar with the skin of said motif housed and held inside; [ Fig 13] et [Fig 14 ] are graphs representing the evolution of stress as a function of deformation during a compression test of lattice-structured structures according to the invention and of a lattice-structured structure according to the prior art. Description détaillée

[0079] For the sake of clarity, the same references designating the same elements according to the state of the art and according to the invention are used for all the figures 1A à 10 .

[0080] THE figures 1A à 2C were described in the description of the prior art.

[0081] We illustrated to figures 3A, 3B And 3C An example of a lattice-structured architectural structure 10 according to the invention. The lattice-structured architectural structure 10 is monolithic and comprises a body lattice 1 and a surface lattice 11 covering the body lattice 1.

[0082] The lattice of body 1 is similar to the lattice 1 described in the preamble and illustrated in the figures 1A et 1B The lattice of body 1 comprises a plurality of elementary motifs of body 2 repeated periodically in space and in contact with each other. The elementary motifs of body 2 are of the rhombic dodecahedral type, as previously described and illustrated in figures 2A, 2B et 2C Also, all the characteristics already described concerning lattice 1 and the elementary rhombic dodecahedral type motifs 2 of the figures 1A à 2C are applicable to the lattice of body 1 and to the elementary motifs of body 2.

[0083] The surface lattice 11 comprises a plurality of surface elementary motifs 12 repeated periodically in a plane P. The surface elementary motifs 12 are each in contact and connected with the body lattice 1.

[0084] We illustrated to figures 4A à 4C a superficial elementary motif 12 of the superficial lattice 11 of the figures 3A, 3B And 3C . Such a superficial elementary motif 12 comprises four feet 13 and a support block 14.

[0085] Each of the feet 13 consists of a single branch comprising an end 13a fixed to the support block 14. The single branch of the foot 13 also includes another end 13b, opposite end 13a and fixed to the body strands 3 of the body lattice 1 forming one of the acute-angled vertices 5 of the rhombic dodecahedron 4, as illustrated by aux figures 3A And 3C . The other end 13b is common to each of the feet 13 of the superficial elementary motif 12.

[0086] Between end 13a and the other end 13b, each foot 13 follows a curved line contained in a plane Q perpendicular to plane P. Thus, as illustrated in the figure 4B , each of the feet 13 extends in a straight line when viewed orthogonally to plane P. The feet 13 are concave when viewed from the support block 14.

[0087] The tangent Ta of the curved line formed by foot 13 at end 13a forms an angle αa with plane P equal to 90°. The tangent Tb of the curved line formed by foot 13 at end 13b is parallel to plane P. The inclinations of the tangents Ta and Tb with respect to plane P influence the flexibility of foot 13.

[0088] The curved line at each foot 13 can be a quadratic Bézier curve. The quadratic Bézier curve is defined by the formula: B t = 1 − t 2 P 0 + 2 t 1 − t P 1 + t 2 P 2 , in which, t is a positive real number between 0 and 1, P 0 is the initial control point of the quadratic Bézier curve located at end 13b, P 2 is the final control point of the quadratic Bézier curve located at end 13a and P 1 is an intermediate control point of the Bézier curve.

[0089] The Bézier curve does not pass through the intermediate control point P1. The tangents Ta and Tb pass through the intermediate control point P1 of the Bézier curve. The intermediate control point P1 is located according to the desired flexibility of foot 13. In particular, the further the intermediate control point P1 is from the segment connecting the initial control point P0 and the final control point P2, the greater the curvature of foot 13 and therefore the more flexible it is. Preferably, the intermediate control point P1 is positioned so that the tangent Tb is parallel to plane P.

[0090] We illustrated to figures 5, 6 And 7 methods of realization of an architecturally structured lattice 10 presenting different positions of the intermediate control point P 1 of the quadratic Bézier curve.

[0091] In the example illustrated by the figure 5 The intermediate control point P1 is close to the end 13b common to each of the feet 13. In the example illustrated by the figure 6 The intermediate control point P1 is located away from the end 13b common to each of the feet 13 such that the tangent Ta is normal to plane P. In the example illustrated by the figure 7 , the intermediate control point P 1 is closer to the end 13b common to each of the feet 13 compared to the example illustrated by the figure 6 Thus, feet 13 of the embodiment of the figure 5 are more rigid than feet 13 of the embodiment of the figure 6 which are more rigid than feet 13 of the embodiment of the figure 7 .

[0092] Alternatively, the curved line at each foot 13 can be a Bézier curve of degree greater than two. For example, the Bézier curve can be of degree three and defined by the formula: B t = 1 − t 3 P 0 + 3 P 1 t 1 − t 2 + 3 P 2 t 2 1 − t + P 3 t 3 , in which, t is a positive real number between 0 and 1, P0 is the initial control point of the quadratic Bézier curve located at endpoint 13b, P3 is the final control point of the quadratic Bézier curve located at endpoint 13a, and P1 and P2 are intermediate control points of the Bézier curve. The Bézier curve does not pass through the intermediate control points P1 and P2.

[0093] The tangent Tb passes through the intermediate control point P 1 of the Bézier curve and the tangent Ta passes through the intermediate control point P 2 of the Bézier curve.

[0094] Each foot 13 can also be characterized by distances h and r, measured orthogonally, respectively parallel, to plane P, between end 13a and the other end 13b. Distances h and r are each chosen according to the desired deformation behavior under a compressive force normal to plane P applied to the support block 14. Distance r, in particular, influences the stiffness of the foot 13. The greater the distance r, the more flexible the foot 13, i.e., the more easily it flexes. Preferably, distance r is chosen such that the surface truss 11 has a modulus of elastic stiffness less than or equal to the modulus of elastic stiffness of the body truss 1. Distance h, in particular, influences the amplitude of the translational displacement of the support block 14 along an axis parallel to the compressive force. The greater the distance h, the greater this amplitude.The distance h is the same for each of the feet 13 so that the support block 14 remains parallel to the plane P under the effect of a compressive force normal to the plane P.

[0095] The support block 14 extends in the plane P, called the median plane P. The support block 14 comprises a set of reinforcement beams 151, 152, connected together to form a reinforcement 16. The support block 14 also comprises a skin 17 carried and fixed on the reinforcement 16.

[0096] The reinforcement 16 is parallel to the median plane P. It is of convex hexagonal and irregular shape. In particular, the reinforcement beams 15 1 closest to the connecting strands 7 of the elementary body motif 2 to which the surface elementary motif 12 is attached are shorter in length than the other reinforcement beams 15 2. In addition, the ends 13a of the feet 13 are attached to said shorter reinforcement beams 15 1.

[0097] The reinforcement 16 is centered around a reinforcement axis Y normal to the median plane P. The reinforcement is invariant under rotation by an angle π / 2 around the reinforcement axis Y. Similarly, the feet 13 are invariant under rotation by an angle π / 2 around the reinforcement axis Y.

[0098] As illustrated in the figure 8 , in which the lattice-structured architecture of 10 of figures 3A, 3B And 3Cis represented without the skins 17, the reinforcement 16 of a surface element 12 has a complementary shape to the body element 2 to which the feet 13 of the surface element 12 are attached. Viewed orthogonally to the median plane P, the reinforcement 16 surrounds the body strands 3 forming the vertex 5 of the rhombic dodecahedron 4 closest to said reinforcement 16. Furthermore, viewed orthogonally to the median plane P, the connecting strands 7 are arranged outside the reinforcement 16. In particular, viewed orthogonally to the median plane P, the reinforcement beams 15 1 are superimposed on the connection points 6 between the connecting strands 7 and the body strands 3. Starting from the reinforcement 16 and following a normal to the median plane P, the points of the body element 2 closest to the reinforcement 16 are the connection points 6. The distance, measured orthogonally to the median plane P, between the armature 16 and the elementary motif of body 2 is thus maximized.Thus, when the feet 13 are deformed by a compressive force with the end 13a arranged in the elementary cell of body 8, the reinforcement 16 remains distant from the strands of body 3 and the bonding strands 7.

[0099] Furthermore, as illustrated in the figure 8 , viewed orthogonally to the median plane P, each foot 13 of a superficial elementary motif 12 is distant from the nearest foot 13 of the nearest adjacent superficial elementary motif 12 by a distance d greater than 1 mm.

[0100] In the embodiment illustrated in figures 3A, 3B And 3CThe skin 17 of each of the surface element motifs 12 is separate from the skins 17 of the adjacent surface element motifs. Viewed orthogonally, the skin 17 has an outer perimeter in the shape of a convex and irregular hexagon. In particular, the shape of the outer perimeter of the skin 17 is an enlargement of the outer perimeter of the reinforcement 16. Thus, the skin 17 is shaped to be distant from the bonding strands 7 when the feet 13 are deformed by the compressive force and the end 13a is contained within the body element cell 8.

[0101] The skin 17 includes a central opening 18 that passes completely through its thickness. The central opening 18 is opposite, that is, aligned orthogonally to the median plane P, the end 13b common to each of the feet 13. The central opening 18 is therefore also opposite the vertex 5 of the rhombic dodecahedron 4 closest to the skin 17. The central opening 18 may be in the shape of a convex and irregular hexagon. In particular, the outer edge of the central opening 18 may be a reduction of the inner edge of the frame 16.

[0102] The superficial elementary motif 12 is inscribed in a superficial elementary cell 19, which corresponds to the smallest rectangular parallelepiped circumscribed about the superficial elementary motif 12.

[0103] The surface elementary cell 19 comprises a face 19a including the end 13b common to each of the feet 13 at its center. The face 19a is contained within one of the faces of the body elementary cell 8, being concentric with said face of the body elementary cell 8. Viewed orthogonally to the median plane P, the feet 13 form an X, more specifically a St. Andrew's cross.

[0104] The surface elemental patterns 12 define an outer face 20 of the structure 10. This outer face 20 is parallel to plane P. The surface lattice 11 has a contact surface 21 defined as the set of points of the structure 10 of the surface enveloping the outer face 20. The contact surface 21 is composed of the surface of the skin 17 included in face 19b of the surface elemental cell 19 opposite face 19a. Thus, the contact surface 21 of the surface lattice 11 is larger than the contact surface 9 of the body lattice 1. Furthermore, the contact surface 21 of the surface lattice 11 is free of sharp points. Thus, the feeling of comfort for a user leaning on a lattice-structured architecture 10 comprising a body lattice 1 and the surface lattice 11 covering the body lattice 1 is improved.

[0105] In the case where the support block 14 consists solely of the reinforcement 16, the contact surface 21 is the surface of the reinforcement 16 located on face 19b of the surface element 19 opposite face 19a. The contact surface 21 of the surface truss 11 is then larger than the contact surface 9 of the body truss 1. Furthermore, the contact surface 21 of the surface truss 11 is free of sharp edges. Thus, the perceived comfort for a user leaning on a truss-structured framework 10 comprising a body truss 1 and the surface truss 11 covering the body 1 truss is improved.

[0106] We illustrated to figures 9A et 9B Another example of a lattice-structured architectural structure 10 according to the invention. The lattice-structured architectural structure 10 of figures 9A et 9B differs from that of figures 3A, 3B And 3Cin that the skins 17 of the various surface elemental motifs 12 are rigidly joined to one another. The skin 17 of each surface elemental motif 12 comprises contact points 23 fixed rigidly to the contact points 23 of the adjacent skins 17. The contact points 23 are located near the vertices of face 19b of the surface elemental cell 19. Furthermore, each skin 17 comprises grooves 24 extending opposite one of the bonding strands 7. Thus, during a translation of the support block 14 orthogonally to the median plane P, the bonding strands 7 do not come into contact with the skin 17.

[0107] The lattice-structured architecture of 10 figures 9A et 9B also differs from that of figures 3A, 3B And 3Cin that, for each foot 13, the plane Q comprising the curved line followed by said foot 13 is oblique to the plane P. Said plane Q forms an angle of inclination θ with the plane P less than 90°. Thus, as illustrated in the figure 10 , in which the lattice-structured architecture of 10 of figures 9A et 9B is represented without the skins 17, each of the feet 13 extends in a curvilinear manner when viewed orthogonally to plane P.

[0108] We illustrated at the figure 11 Another example of a lattice-structured architectural structure 10 according to the invention. The lattice-structured architectural structure 10 of the figure 11 differs from that of figures 3A, 3B And 3C in that the 13 feet do not extend along a curved line, being a quadratic Bézier curve. The 13 feet of the truss-structured architecture 10 of the figure 11 extend along a three-dimensional curved line, the curved line being a cubic Bézier curve defined by equation [Math 3]. The intermediate control point P1 of the Bézier curve is located such that the tangent Tb is parallel to the median plane P. The intermediate control point P2 of the Bézier curve is located such that the tangent Ta is normal to the median plane P.

[0109] We illustrated to figures 12A et 12B Another example of a lattice-structured architectural structure 10 according to the invention. The lattice-structured architectural structure 10 of figures 12A et 12B differs from that of figures 3A, 3B And 3Cin that the reinforcement 16 of each surface element 12 comprises a set of reinforcing beams 15 3 connected to each other to form a first square and a set of reinforcing beams 15 4 connected to each other to form a second square arranged within the first square. The first and second squares are concentric and include the median plane P. The reinforcement 16 also includes interconnecting beams 33 connecting the vertices of the first square to the vertices of the second square. The ends 13a of the feet 13 are fixed to the reinforcing beams 15 3 forming the first square. The skin 17 of each surface element 12 is housed within, and supported by, the reinforcing beams 15 4 forming the second square, conforming to the shape of said square. The skin 17 is also included in the median plane P.Thus, the contact surface 21 of the surface lattice 11 includes, in addition to the surface of the skin 17, the surface of the reinforcement 16 contained in face 19b of the surface elementary cell 19 opposite face 19a. It is possible to vary the percentage of the face of the surface elementary motif 12, viewed orthogonally to the median plane P, covered by the skin 17 by decreasing or increasing the distance between the first and second squares. Exemple 1

[0110] The inventors carried out a first series of comparative compression tests on lattice-structured structures similar to the one illustrated in the figures 12A et 12B and of representative lattice-structured architectural models consisting solely of a body 1 lattice. The elementary body 2 motifs of the representative lattice-structured architectural models are identical to the elementary body 2 motifs of the body 1 lattice of the lattice-structured architectural model 10 illustrated in figures 2A, 2B et 2C For each of the tested lattice structures, the elementary cells of body 8 are cubes with sides of 15 mm, the strands of body 3 and the connecting strands 7 have a diameter of 1.0 mm, the lattice of body 1 is composed of three superimposed square layers, each comprising five rows of five aligned elementary motifs of body 2. For each of the tested lattice structures 10 according to the invention, the feet 13 have a diameter of 0.9 mm, for each foot 13, the distance h, measured orthogonally to plane P, between end 13a and the other end 13b is equal to 6 mm, and the intermediate point P1 of the quadratic Bézier curve is 7.3 mm from the end 13b common to each of the feet 13.Furthermore, all the lattice-structured architectural elements are monolithic and made of thermoplastic polyurethane (TPU), said lattice-structured architectural elements being obtained by additive manufacturing on a powder bed, by "Multi Jet Fusion".

[0111] The compression tests were carried out in a direction normal to the plane P in which the surface lattice 11 extends. For each of the lattice-structured structures tested, the compression test consists of the application of a preload of 2 N followed by four compressions at a rate of displacement along an axis parallel to the reinforcement axes Y of 5 mm / min until a deformation of 70% then a fifth compression at a rate of 1 mm / min.

[0112] We illustrated at the figure 13 The results of the fifth compression tests are shown in graph 25, showing stress vs. strain. Graph 25 includes a curve 26 representing the average stress-strain value of the compression tests of three control lattice structures produced by the same 3D printing process. Graph 25 also includes curves 27 and 28, each representing the average stress-strain value of the compression tests of three examples of lattice structures 10 according to the invention produced by the same 3D printing process.Furthermore, the percentage of the face of the superficial elementary motif, viewed orthogonally to the median plane P, covered by the skin 17 of each superficial elementary cell 19 of the lattice-structured architectures 10 tested for curve 27 is greater than the percentage of the face of the superficial elementary motif, viewed orthogonally to the median plane P, covered by the skin 17 of each superficial elementary cell 19 of the lattice-structured architectures 10 tested for curve 28.

[0113] As observed in Figure 25, for the same deformation of less than 20%, the stress in the structures 10 according to the invention is lower than the stress in the control structures. This is evidenced by the difference in stress, at a fixed deformation, between curve 26 and curve 27 or 28. In other words, for this range of deformations, the structures 10 according to the invention are more flexible than the control structures. Thus, the presence of a surface truss 11 on a body truss 1 of the truss-structured structure 10 according to the invention provides improved comfort for the user resting on said structure 10 for deformations of less than 20%. Exemple 2

[0114] The inventors carried out a second series of comparative compression tests on lattice-structured architectures similar to the one illustrated in the figure 11 and of representative lattice-structured architectural models consisting solely of a body 1 lattice. The elementary body 2 motifs of the representative lattice-structured architectural models are identical to the elementary body 2 motifs of the body 1 lattice of the lattice-structured architectural model 10 illustrated in figures 2A, 2B et 2C For each of the tested lattice structures, the elementary cells of body 8 are cubes with sides of 15 mm, the strands of body 3 and the connecting strands 7 have a diameter of 1.0 mm, the lattice of body 1 is composed of three superimposed square layers, each comprising five rows of five aligned elementary motifs of body 2. For each of the tested lattice structures 10 according to the invention, the feet 13 have a diameter of 0.9 mm, and for each foot 13, the distance h, measured orthogonally to plane P, between end 13a and the other end 13b is equal to 6 mm. Furthermore, all the lattice structures are monolithic and made of thermoplastic polyurethane (TPU), said lattice structures being obtained by additive manufacturing on a powder bed, by "Multi Jet Fusion".

[0115] The compression tests were carried out in a direction normal to the plane P in which the surface lattice 11 extends. For each of the lattice-structured structures tested, the compression test consists of the application of a preload of 2 N followed by four compressions at a rate of displacement along an axis parallel to the reinforcement axes Y of 5 mm / min until a deformation of 70% then a fifth compression at a rate of 1 mm / min.

[0116] We illustrated at the figure 14The results of the fifth compression tests are shown in graph 29, showing stress vs. strain. Graph 29 includes a curve 30 representing the average stress-strain value of the compression tests of three control truss structures produced by the same 3D printing process. Graph 29 also includes curves 31 and 32, each representing the average stress-strain value of the compression tests of three examples of truss structures 10 according to the invention produced by the same 3D printing process. For the truss structures 10 tested for curve 31, the midpoint P1 of the quadratic Bézier curve is 2.8 mm from the end 13b common to each of the legs 13, and the midpoint P2 of the quadratic Bézier curve is 4.0 mm from the end 13a fixed to the support block 14.For the lattice-structured architectures 10 tested for the curve 32, the intermediate point P 1 of the quadratic Bézier curve is 5.4 mm away from the end 13b common to each of the feet 13, and, the intermediate point P 2 of the quadratic Bézier curve is 5.4 mm away from the end 13a fixed to the support block 14.

[0117] As observed in Figure 29, for the same deformation of less than 20%, the stress in the structures 10 according to the invention is lower than the stress in the control structures. This is evidenced by the difference in stress, at a fixed deformation, between curve 30 and curve 31 or 32. In other words, for these small deformations, the structures 10 according to the invention are more flexible than the control structures. Thus, the presence of a surface truss 11 on a body truss 1 of the truss-structured structure 10 according to the invention provides improved comfort for the user resting on said structure 10 for deformations of less than 20%.

[0118] Other variations and improvements can obviously be envisaged without departing from the scope of the invention as defined by the following claims. In particular, although described with a body lattice comprising a plurality of elementary body motifs of the rhombic dodecahedral type, the invention is adaptable for other types of elementary body motifs.

Claims

1. Architectured lattice structure (10) comprising: - a body lattice (1) having a plurality of body unit patterns (2) that are repeated periodically and in contact with one another, each body unit pattern having body strands (3) connected to each other to form the edges of a polyhedron (4) and connecting strands (7) connecting the polyhedron to the vertices of the body unit cell (8), which is the smallest rectangular parallelepiped circumscribing the body unit pattern, - a surface lattice (11) defining a face (20) of the structure and at least partially covering the body lattice, the surface lattice having a plurality of surface unit patterns (12) that are repeated periodically, each surface unit pattern having a supporting block (14) extending in a median plane (P), parallel to the face of the structure defined by the surface lattice, and deformable feet (13) that each have one end (13a), fastened to the supporting block and at a distance from the other feet, and another end (13b), at a distance from the median plane and common to all the other feet and to at least one body strand, the surface lattice being configured so that, under the effect of a compressive force normal to the median plane, the feet deform to move the supporting block in translation along an axis parallel to the compressive force.

2. Structure according to the preceding claim, the feet of each surface unit pattern being separated from one another on their portions between the end fastened to the supporting block and the end common to each of the feet and to at least one body strand.

3. Structure according to any one of the preceding claims, the end common to each of the feet and to at least one body strand being fastened to one of the vertices (5) of the polyhedron, said vertex preferably being included in one of the faces of the body unit cell, said vertex preferably being at the centre of said face of the body unit cell.

4. Structure according to any one of the preceding claims, seen orthogonally to the median plane, the end common to each of the feet and to at least one body strand being equidistant from each of the ends fastened to the supporting block of the surface unit pattern.

5. Structure according to any one of the preceding claims, seen orthogonally to the median plane, each of the ends fastened to the supporting block being equidistant from the other two nearest ends which are fastened to the supporting block.

6. Structure according to any one of the preceding claims, each surface unit pattern having four feet, preferably, seen orthogonally to the median plane, the feet together forming an X-shaped pattern.

7. Structure according to any one of the preceding claims, each foot being symmetrical with at least two adjacent feet, each symmetry being effected with respect to a plane perpendicular to the median plane.

8. Structure according to any one of the preceding claims, each of the feet extending along a curved line, the curved line preferably being a Bézier curve or an arc of an ellipse.

9. Structure according to any one of the preceding claims, each surface unit pattern being inscribed in a surface unit cell (19) of rectangular parallelepiped shape and having a face (19a) included in a face of one of the body unit cells.

10. Structure according to any one of the preceding claims, the supporting block comprising a reinforcement (16) comprising a plurality of reinforcement beams (151, 152) interconnected to form the sides of at least one polygon parallel to the median plane.

11. Structure according to any one of the preceding claims, the supporting block covering at least 50% of the face of the surface unit pattern seen orthogonally to the median plane, the supporting block preferably comprising a skin (17) extending parallel to the median plane and covering at least 50% of the face of the surface unit pattern seen orthogonally to the median plane.

12. Structure according to any one of the preceding claims, the architectured lattice structure being monolithic, preferably made from one and the same material.

13. Structure according to any one of the preceding claims, the polyhedron being a rhombic dodecahedron, the connecting strands preferably connecting the obtuse-angled vertices (6) of the rhombic dodecahedron to the vertices of the body unit cell.

14. Device selected from: - a shock absorber, - a support for the body, for example a seat cushion for seats, a cushion, a mattress, an armrest, a headrest, a helmet liner or a wrist support, and - a holding member, for example a holding handle, or a steering wheel, the device having an architectured lattice structure according to any one of the preceding claims.

15. Method for manufacturing an architectured lattice structure according to any one of Claims 1 to 13 by means of an additive manufacturing technique.