Porous body, additive manufacturing method for the body and apparatus for supporting and/or bearing a person

Abstract

It is a feature of a porous body (10, 20) comprising a three-dimensional network of node points (200) joined to one another by struts (100), and a void volume (300) present between the struts (100), that the struts (100) have an average length of 200 to 50 mm, the struts (100) have an average thickness of 100 m to 5 mm, and that the porous body has a compression hardness (40% compression, DIN EN ISO 3386-1: 2010-09) in at least one spatial direction of 10 to 100 kPa. The porous body according to the invention combines the advantages of a conventional mattress or cushion with ventilatability which results from its porous structure and is not achievable in conventional foams. The invention further relates to a method of producing such a porous body (10, 20) and to an apparatus comprising said body (10, 20) for supporting and/or bearing a person.

Claims

1. A porous body comprising a three-dimensional network of node points joined to one another by struts, and a void volume present between the struts, characterized in that the struts have an average length of 200 m to 50 mm, the struts have an average thickness of 100 m to 5 mm, and in that the body has a compression hardness (40% compression, DIN EN ISO 3386-1: 2010-09) in at least one spatial direction of 10 to 100 kPa.

2. The porous body according to claim 1, wherein the body has a compression set after 40% compression (DIN ISO 815-1) of 5%.

3. The porous body according to claim 1, wherein the body has a tan value (20 C., DMA, DIN EN ISO 6721) in at least one spatial direction of 2:0.1 to:S 1.5 and/or the body has a maximum tan value (DMA, DIN EN ISO 6721) in at least one spatial direction at 10 C. to 40 C.

4. The porous body according to claim 1, wherein the compression hardness (40% compression, DIN EN ISO 3386-1:2010-09) of the body in a selected spatial direction differs by 10% from the compression hardness (40% compression, DIN EN ISO 3386-1:2010-09) of the body in a spatial direction at right angles to the spatial direction selected, and/or the tan value (20 C., DMA, DIN EN ISO 6721) of the body in a selected spatial direction differs by 10% from the tan value (20 C., DMA, DIN EN ISO 6721) of the body in a spatial direction at right angles to the spatial direction selected.

5. The porous body according to claim 1, wherein the compression hardness (40% compression, DIN EN ISO 3386-1:2010-09) of the body in a selected spatial direction differs by <10% from the compression hardness (40% compression, DIN EN ISO 3386-1:2010-09) of the body in other spatial directions and/or the tan value (20 C., DMA, DIN EN ISO 6721) of the body in a selected spatial direction differs by <10% from the tan value (20 C., DMA, DIN EN ISO 6721) of the body in other spatial directions.

6. The porous body according to claim 1, wherein the body is at least partly formed from a material having one or more of the following properties: a tan value (20 C., DMA, DIN EN ISO 6721) of 0.1 to 1.5 a maximum tan value (DMA, DIN EN ISO 6721) of 10 C. to 40 C. a modulus of elasticity (DIN EN ISO 604:2003-12) of 1 MPa to 800 MPa a Shore hardness (DIN ISO 7619-1:2012-02) of 40A to 70D a melting point (DIN EN ISO 11357-3:2013-04) of 220 C. a glass transition temperature T.sub.g(DMA, DIN EN ISO 6721) of 40 C.

7. The porous body according to claim 1, wherein the void volume makes up 50% to 99% of the volume of the body.

8. The porous body according to claim 1, wherein the node points are distributed in a periodically repeating manner in at least part of the volume of the body.

9. The porous body according to claim 1, wherein the void volume is formed in the form of mutually penetrating first, second and third groups of channels, wherein a multitude of individual channels within each respective group of channels run parallel to one another and the first group of channels, the second group of channels and the third group of channels extend in different spatial directions.

10. The porous body according to claim 1, wherein the average minimum angle between adjacent struts is 30 to 140.

11. The porous body according to claim 1, wherein the spatial density of the node points in a first region of the body is different from the spatial density of the node points in a second region of the body.

12. The porous body according to claim 1, wherein the material of the body in a first region of the body is different from the material in a second region of the body.

13. A method of producing a porous body according to claim 1, characterized in that the body is produced in an additive manufacturing method.

14. An apparatus for supporting and/or bearing a person, comprising a porous body according to claim 1.

15. The apparatus according to claim 14, further comprising a ventilator for passing air through at least a portion of the porous body.

Description

(1) The present invention is elucidated in detail by the figures which follow with reference to preferred embodiments, but without being restricted thereto. The figures show:

(2) FIG. 1 a porous body according to the invention in a first view

(3) FIG. 2 the porous body according to the invention from FIG. 1 in another view

(4) FIG. 3 the porous body according to the invention from FIG. 1 in another view

(5) FIG. 4 a further porous body according to the invention

(6) FIG. 5 a porous structure according to example 1 and 2

(7) FIG. 1 shows a porous body 10 according to the invention in perspective view with a three-dimensional network of node points 200 joined to one another by struts 100. Between the struts 100 is the void space 300. At the edges of the body 10, there are truncated node points 201, the struts from which project only into the interior of the body 10. FIG. 2 shows the same body 10 in a first isometric view and FIG. 3 the same body 10 in a further isometric view, corresponding to a top view of one side of the body 10. On the outer faces of the body 10 shown in FIG. 3, there are also truncated node points identified by the reference numeral 202.

(8) The node points 200 in the body 10 according to the invention may be in regular distribution in at least part of its volume. It is likewise possible for them to be in irregular distribution in at least part of its volume. It is also possible that the body 10 has one or more sub-volumes in which the node points 200 are in regular distribution and one or more sub-volumes in which the node points 200 are in irregular distribution.

(9) According to the structure of the network composed of struts 100 and node points 200 in the porous body 10 according to the invention, particular mechanical properties may also be a function of the spatial direction in which they are determined on the body. This is the case, for example, for the body 10 shown in FIGS. 1 to 3. Along the spatial directions corresponding to the base factors of the unit cell, the compression hardness and the tan value in particular may be different than, for example, in a spatial direction including all three base spectres as components.

(10) It is possible that the void volume 300 makes up 50% to 99%, preferably 55% to 95%, more preferably 60% to 90%, of the volume of the body 10. With knowledge of the density of the starting material for the body and the density of the body itself, it is easily possible to determine this parameter.

(11) Preferably, the node points 200 in at least part of the volume of the body 10 are in periodically repeating distribution. When the node points 200 in a volume are in periodically repeating distribution, this circumstance can be described by the means of crystallography. The node points may be arranged in accordance with the 14 Bravais lattices: simple cubic (sc), body-centred cubic (bcc), face-centred cubic (fcc), simple tetragonal, body-centred tetragonal, simple orthorhombic, base-centred orthorhombic, body-centred orthorhombic, face-centred orthorhombic, simple hexagonal, rhombohedral, simple monoclinic, base-centred monoclinic and triclinic. Preference is given to the cubic lattices sc, fcc and bcc.

(12) Persisting with the crystallographic view, the number of struts 100 via which one node point 200 is connected to other node points can be regarded as the coordination number of the node point 200. The average number of struts 100 that proceed from the node points 200 may be 4 to 12, but it is also possible to achieve coordination numbers that are unusual or are impossible in crystallography. For the determination of the coordination numbers, truncated node points on the outer face of the body, as given by reference numeral 201 in FIG. 1, are not taken into account.

(13) The presence of unusual coordination numbers or those that are impossible in crystallography can especially be achieved when the porous body according to the invention is produced by means of additive manufacturing techniques. It is likewise possible that a first group of node points 200 has a first average number of struts 100 and a second group of node points has a second average number of struts 100, where the first average number is different from the second average number.

(14) In body 10 shown in FIGS. 1 to 3, the node points 200 are arranged in a body-centred cubic lattice. The coordination number and hence the average number of struts that proceed therefrom is 8.

(15) It is possible that the average minimum angle between adjacent struts 100 is 30 to 140, preferably 45 to 120, more preferably 50 to 100. In the case of the body 10 shown in FIGS. 1 to 3, at all points, the minimum angle between the struts 100 is about 70.5 (arccos()), as can be inferred from trigonometric considerations relating to the angle between the spatial diagonals of a cube.

(16) The structure of the porous body according to the invention may, at least in cases of regular arrangement of the node points 200 in the space, also be described as the result of penetration of hollow channels through a formerly solid body 20. Thus, with reference to FIG. 4, the cavity 300 may take the form of mutually penetrating first 310, second 320 and third 330 groups of channels, where a multitude of individual channels 311, 321, 331 within each respective group of channels run parallel to one another and the first group of channels 310, the second group of channels 320 and the third group of channels 330 extend in different spatial directions.

(17) The body 20 shown in FIG. 4 has, in its section shown to the left of the figure, a higher spatial density of node points 200 than in the section shown to the right of the figure. For better illustration, the aforementioned embodiment is discussed with reference to the section shown on the right. An array 310 of individual channels 311, the direction of which is specified by arrows, extends through the body at right angles to the face of the body facing toward it. It is of course not just the three channels identified by reference numerals but all channels that extend through the body at right angles to the face specified.

(18) The same applies to the channels 321 of the group of channels 320 and the channels 331 of the group of channels 330, which run at right angles to one another and at right angles to the channels 311 of the first group of channels 310. The material of the body which remains between the mutually penetrating channels 311, 321, 331 forms the struts 100 and node points 200.

(19) It is possible that the individual channels 311, 321, 331 have a polygonal or round cross section. Examples of polygonal cross sections are trigonal, tetragonal, pentagonal and hexagonal cross sections. FIG. 4 shows square cross sections of all channels 311, 321, 331. It is also possible that the individual channels 311, 321, 331 within the first 310, second 320 and third 330 group of channels each have the same cross section. This is shown in FIG. 4.

(20) It is likewise possible that the cross section of the individual channels 311 of the first group of channels 310, the cross section of the individual channels 321 of the second group of channels 320 and the cross section of the individual channels 331 of the third group of channels 330 are different from one another. For example, the channels 311 may have a square cross section, the channels 321 a round cross section, and the channels 331 a hexagonal cross section. The cross section of the channels determines the shape of the struts 100, and so, in the case of different cross sections, different characteristics of the body 20 can also be achieved depending on the spatial directions.

(21) In one variant, the spatial density of the node points 200 in a first region of the body 20 may be different from the spatial density of the node points 200 in a second region of the body 20. This is shown in schematic form in the one-piece body 20 according to FIG. 4. As already mentioned, the body 20 shown therein has a higher spatial density of node points 20 in its section shown to the left of the figure than in its section shown to the right of the figure. Only every second node point 200 in the left-hand section forms a strut 100 to a node point 200 in the right-hand section.

(22) FIG. 5 is described in connection with the Examples as follows in the Experimental part.

EXPERIMENTAL PART

Examples

(23) The materials and filaments according to the present invention which were used in the following experiments, have been produced by extrusion of the raw materials (in form of granules, pellets, powder or cut in coarse material with a maximum diameter of 4 to 6 mm) at temperatures below 240 C. into filaments with a diameter of 1.75 mm.

(24) The Thermoplastic Polyurethane (TPU) filaments according to the present invention with a diameter of 1.75 mm have been produced by extrusion of a TPU grade based on an aliphatic isocyanate ether/ester-hybrid type with a hardness of Shore 85 A and a TPU grade based on an aromatic isocyanate ester type with a hardness of Shore 90 A, respectively.

(25) All filaments have been dried prior to use for 24 h at 30 C. in a vacuum drying cabinet.

(26) Two porous bodies according to the invention were manufactured using an additive manufacturing process and their compression hardness was measured.

Example 1

(27) A porous body was manufactured using the additive manufacturing process of fused deposition modelling (FDM). The build material was a thermoplastic polyurethane (TPU) filament, made by extrusion of pellets of a TPU grade based on an aromatic isocyanate ester type with a hardness of Shore 90 A into a round filament with 1.75 mm diameter. This filament was fed into a DD3 extruder mounted on a Prusa 13 printer. The nozzle temperature of the DD3 extruder was set to 235 C. and the print speed to 25 mm/s.

(28) The porous body was printed layer-by-layer using the TPU filament according to a section of the scaffold structure as shown in FIG. 5 as a cube with an edge length L of 30 mm, a bar width 110 of 2.5 mm and a distance 120 between nodes 200 of the body-centred lattice of 4.5 mm. The section of the scaffold structure was chosen in a manner that all bars end at the faces of the cube in truncated nodes 202 and at the edges of the cube in truncated nodes 201.

(29) The compression hardness of the as manufactured porous body was measured on the basis of DIN EN ISO 3386-1:2010-09 using an Instron 5566 machine from Instron GmbH, Germany. The measurement was performed at room temperature (23 C.) and a traverse speed of 100 min/min. The porous body was consecutively compressed 3 times by 40% (corresponding to a residual height L0 of 60%=1.8 cm compared to height L of 3 cm of the uncompressed cube) and relaxed immediately using the same traverse speed. Afterwards, the porous structure was compressed for a fourth time by 40% and the used force for this compression is recorded. The value is given in Table 1.

Example 2

(30) A porous body as of example 1 was manufactured, however, using a filament made out of a TPU grade based on an aliphatic isocyanate ether/ester-hybrid type with a hardness of Shore 85 A. The printer settings are equal to the ones given in example 1 and the compression hardness measurement was performed as described in example 1.

(31) TABLE-US-00001 TABLE 1 compression strength investigation based on DIN EN ISO 3386-1: 2010-09 TPU grade TPU grade of Ex. 1, of Ex. 2, Material Shore A 90 Shore A 85 width [mm] 29.8 28.7 length [mm] 28.3 28.2 hight [mm] 28.3 29.1 area [mm.sup.2] 800.9 820.6 volume [mm.sup.3] 23866.5 23551.8 weight [g] 4.1550 3.7200 density [g/cm.sup.3] 0.1741 0.1579 force for 40% 25.3 18.9 compression [N] modulus [N/mm.sup.2] 0.0316 0.0230 or Mpa modulus [kPa] 31.6 23.0

(32) It can be clearly observed, that suitable combinations of 3D printed inventive geometry design and materials with a material hardness (Shore A)98 according to the invention in combination with the inventive void density and distribution yield excellent mechanical results and perfectly target a 40% compression, DIN EN ISO 3386-1:2010-09 of 10 to 100 kPa.