Manufacturing process for a mattress

Abstract

A continuous method for manufacturing a mattress (10) comprising: extruding a thermoplastic polymer (P) through an extrusion die (2) comprising extrusion nozzles (5) distributed along a lengthwise direction (L1) and a widthwise direction (L2) of the extrusion die (2), generating a curtain (3) of continuous fused fibers (4), falling by gravity, passing said curtain (3) of continuous fused fibers (4) between two counter-rotating guide members (6), generating a 3D entanglement (7) of irregularly arranged fibers with loop fusion between the continuous fibers and in a layer of total thickness (et) determined by the center distance (d1) between said two counter-rotating guide members (6), the counter-rotating guide members (6) being arranged relative to each other and relative to the extrusion die (2) such that the generated 3D entanglement (7) exhibits,on a first layer (e1) extending from a first face (8), a first fiber density, and, on a second layer (e2) extending from a second face (9) opposite the first face (8), a second fiber density greater than said first fiber density, solidification of the 3D fiber entanglement (7) by immersion in a coolant (B) to form the padding (10). Figure from the abstract: Figure 1,

Description

Title of the invention: Method for manufacturing a mattress technical field

[0001] This disclosure relates to a method for manufacturing padding, in particular for a motor vehicle seat. This disclosure also relates to an installation for carrying out the method, as well as padding obtained by such a method, a motor vehicle seat component incorporating such padding, and a motor vehicle seat incorporating such a seat component. Previous technique

[0002] Vehicle seat components, particularly for automobiles, each comprise at least a frame and padding. Vehicle seat components, especially the seat cushion, may also include a reinforcing fabric placed between the frame and the padding to reduce wear on the padding and increase its lifespan. Finally, vehicle seat components may include a cover, which serves a finishing function, covering the padding to form what is commonly called the upholstery. All these constituent elements of vehicle seat components, such as the backrest or the seat cushion, are assembled together during installation. There is a need to reduce the number of steps required during the assembly of seat components and the number of parts needed to manufacture these seat components.

[0003] Furthermore, the padding of vehicle seat components, particularly automotive seats, is conventionally made of urethane polymer foam (or polyurethane, PU), specifically polyurethane foam obtained from polyether / polyol (or PUR) type polyols. Such foams can be relatively easily shaped in molds to form different padding shapes for various vehicle seat components, such as the seat cushion, backrest, armrest, or headrest, for example.

[0004] Polyurethane foam padding is satisfactory, but can retain moisture, particularly in humid conditions. This can cause discomfort for an occupant of a vehicle seat containing such padding.

[0005] Furthermore, polyurethane foam is conventionally produced by mixing, among other things, polyols with isocyanates. The chemical reaction carried out emits CO2 to form a foam, and the emitted CO2 contributes to global warming.

[0006] Furthermore, polyurethane foam is not recyclable.

[0007] Also, it appears desirable, at least from an ecological point of view, to limit the use of polyurethane in the padding of vehicle seat components.

[0008] Furthermore, there is a need to reduce the mass of a vehicle seat. Summary

[0009] This disclosure improves the situation.

[0010] A continuous process for manufacturing a mattress is proposed, comprising: - extrusion of a thermoplastic polymer in an extrusion die comprising extrusion nozzles distributed along a longitudinal direction and along a widthwise direction of the extrusion die, generating a curtain of continuous molten fibers, falling by gravity, - passage of said curtain of continuous fused fibers between two counter-rotating guide members, with a generation of a 3D entanglement of irregularly arranged fibers with fusion of loops between the continuous fibers and according to a layer of total thickness determined by the center distance between said two counter-rotating guide members, the counter-rotating guide members being arranged relative to each other and relative to the extrusion die such that the generated 3D entanglement has, on a first thickness extending from a first face, a first fiber density, and, on a second thickness extending from a second face opposite to the first face, a second fiber density greater than said first fiber density, - solidification of the 3D fiber entanglement by immersion in a cooling liquid to form the padding.

[0011] The process makes it possible to obtain a padding comprising a part including one of the faces with a density such that it forms a denser and more rigid crust, while the rest of the padding remains flexible.

[0012] The features described in the following paragraphs may optionally be implemented independently of each other or in combination with each other:

[0013] The curtain advantageously comprises a plurality of rows of continuous fused fibers, each row extending along the longitudinal direction of the extrusion die, the rows being arranged side-by-side along the widthwise direction of the extrusion die and comprising two end rows. The method preferably comprises receiving the curtain of continuous fused fibers falling by gravity: - between the said two counter-rotating guiding elements for a first part rows of said curtain so as to generate said first fiber density and - on only one of said two counter-rotating guide members for a second part of the rows of said curtain comprising one of the two end rows and possibly at least one adjacent row from said end row so as to generate said second fiber density.

[0014] By end row, we mean a row having only one adjacent row.

[0015] The fact that at least one row is received on one of the counter-rotating guide members and not between the counter-rotating guide members results in its displacement towards an adjacent row at the time the 3D entanglement is generated, specifically before passing between the counter-rotating guide members and before solidification. Thus, the density of these rows within the 3D entanglement is increased relative to the rest of the 3D entanglement. This makes it possible to obtain the crust that extends from the second face and over said second thickness.

[0016] The second thickness, also called crust thickness, can be between 1 mm and 15 mm, in particular between 3 mm and 8 mm.

[0017] In a particular example, said second part of the rows comprises a single row of said curtain, namely said one of the two end rows. In this case, the second thickness is relatively small, being for example between 1 mm and 5 mm, in particular between 3 mm and 5 mm.

[0018] In another particular example, said second part of the rows comprises several rows of said curtain, in particular between two and four rows, namely said one of the two end rows and at least one, in particular between one and three, adjacent rows starting from said one of the two end rows. In this case, the second thickness is, for example, between 3 mm and 15 mm, in particular between 5 mm and 10 mm.

[0019] By "the reception of the continuous fused fiber curtain between said two guiding members [...] and on only one of said two guiding members [...]", it is understood that no receiving or guiding element for the continuous fused fibers forming the curtain is arranged between the extrusion die and the counter-rotating guiding members.

[0020] The two counter-rotating guide members may each comprise a roller, in particular cylindrical or stepped or cylindrical-stepped, or a cam system. In this case, the two counter-rotating guide members may form two conveyors, each comprising, in addition to the said roller, a lower roller located below the said roller at a non-zero distance from it, as well as a belt surrounding and connecting the said roller and the said lower roller and forming the contour of the conveyor. The conveyors are advantageously arranged parallel to each other. The belt of each conveyor is preferably permeable to the coolant, so as to allow the coolant to pass through the belt. The belt is, for example, made of chainmail.

[0021] The rollers are advantageously partially immersed in the coolant to a height less than or equal to half the total height of said %. Thus, the contact between the molten fibers and said only one of said two counter-rotating guide members takes place outside the coolant.

[0022] Alternatively, the rollers may be non-immersed.

[0023] The method may include adjusting the center distance between said counter-rotating guide elements so that said center distance is less than the width of the curtain exiting the extrusion die. Such an adjustment may consist of bringing at least one of said counter-rotating guide elements closer to the other, for example by a distance of between 1 mm and 15 mm, depending on the desired second density. The higher the desired second density, the greater the distance from the guide elements will be, i.e., the smaller the center distance will be.

[0024] The total thickness of the 3D entanglement can be constituted by the first thickness plus the second thickness. The first thickness preferably forms at least 85%, or even at least 90%, of the total thickness. The second thickness can form between 1% and 15% of the total thickness, in particular between 3% and 8% of the total thickness.

[0025] The second density can be greater than or equal to two, or even three or four times the first density approximately.

[0026] The process may further include, after solidification, cutting the solidified 3D entanglement to form the padding itself.

[0027] According to another aspect, in combination with the above, an installation is proposed for implementing the process defined above, comprising: - an extrusion die comprising extrusion nozzles distributed along a longitudinal direction and along a widthwise direction of the extrusion die, configured to generate a curtain of continuous molten fibers, falling by gravity, - two counter-rotating guide members arranged relative to each other so that the center distance between said counter-rotating guide members is less than the width of the curtain that will be generated at the exit of the extrusion die, the counter-rotating guide members being arranged under the extrusion die so as to receive said curtain of continuous molten fibers falling by gravity: • between said two counter-rotating guide members for a first part of the rows of said curtain so as to generate said first fiber density and • on only one of said two counter-rotating guide members for a second part of the rows of said curtain comprising one of the two end rows and possibly at least one adjacent row from said end row so as to generate said second fiber density, - a coolant reservoir.

[0028] The installation may include a cutting system configured to cut the safety mattress produced during the implementation of the process.

[0029] The installation may include one or more guide rollers to guide the 3D entanglement generated after solidification in the coolant basin.

[0030] The two counter-rotating guide members may each comprise a roller, in particular cylindrical or stepped or cylindrical-stepped, or a cam system. In this case, the two counter-rotating guide members may form two conveyors, each comprising, in addition to the said roller, a lower roller located below the said roller at a non-zero distance from it, as well as a belt surrounding and connecting the said roller and the said lower roller and forming the contour of the conveyor. The conveyors are advantageously arranged parallel to each other. The belt of each conveyor is preferably permeable to the coolant, so as to allow the coolant to pass through the belt. The belt is, for example, made of chainmail.

[0031] The rollers are advantageously partially immersed in the coolant to a height less than or equal to half their total height. Thus, the contact between the molten fibers and only one of the two counter-rotating guide members occurs outside the coolant.

[0032] Alternatively, the rollers may be non-immersed.

[0033] The two counter-rotating guide members are preferably driven in rotation at a speed typically lower than the falling speed of the fibers, ensuring an accumulation of fibers which leads to the formation of loops which heat-weld between fibers, generating the irregular three-dimensional entanglement.

[0034] According to another aspect, in combination with the above, a safe mattress is proposed obtained by implementing the process as defined above, comprising a 3D entanglement having, on a first thickness extending from a first face, a first fiber density, and, on a second thickness extending from a second face opposite to the first face, a second fiber density greater than said first fiber density.

[0035] According to another aspect, in combination with the above, a motor vehicle seat element is proposed, in particular a seat or a backrest, comprising a frame and padding obtained using the process as defined above.

[0036] This provides a padding made of a material other than polyurethane foam. Advantageously, this padding material is a recyclable plastic, and its production generates less CO2 emissions than the production of polyurethane foam, thus reducing the environmental impact of the seat element incorporating this padding. In addition to the environmental benefits, the seat element using this padding material can be significantly lighter than a similar polyurethane foam padding. Furthermore, the padding material can be more breathable, allowing better air and moisture to pass through the padding.

[0037] In a particular example, said second face is disposed on the side of the reinforcement. In this case, said second fiber density can be between two and four times said first fiber density. The first face then exhibits a normal irregularity while the second face exhibits a crust, which is denser and harder.

[0038] In this case, the seat element may be without reinforcing fabric, the resulting shell being sufficiently rigid to form an intrinsic reinforcement within the padding. The number of constituent parts of the seat element is then reduced.

[0039] In another specific example, said second face is arranged to be in contact with a user or with a head covering. In this case, said second fiber density may be approximately twice said first fiber density.

[0040] In this case, the shell remains relatively flexible and thin, increasing the density of the padding only at the surface without imparting excessive rigidity. The first face exhibits normal irregularity, while the second face exhibits less irregularity, or even greater regularity, due to its higher fiber density, the added fibers filling the gaps. The quality of the second face is thus improved to meet automotive quality standards.

[0041] The seat element can be chosen from the group consisting of a backrest, in particular of a seat or bench, an armrest, a seat, in particular of a seat or bench, a headrest, a console, in particular central or rear, a part of these and an assembly of all or part of these.

[0042] According to another aspect, in combination with the above, a vehicle seat, in particular a motor vehicle seat, is proposed, comprising at least one seat element as defined above. Brief description of the drawings

[0043] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0044] [Fig-1] is a schematic and partial cross-sectional view of an installation according to a example with implementation of a process according to an example.

[0045] [Fig.2] shows a detail II of [Fig.1].

[0046] [Fig.3] is a schematic and perspective view of the installation according to an example with implementation of the process according to an example.

[0047] [Fig.4] shows, in schematic view, in cross-section, an example of padding obtained at using the method illustrated in figures 1 and 2.

[0048] [Fig. 5] is a schematic partially exploded cross-sectional view of an example of motor vehicle seat.

[0049] [Fig.6] is a schematic and partial cross-sectional view of an installation according to a example with implementation of a process according to an example.

[0050] [Fig.7] shows a detail VII of [Fig.6].

[0051] [Fig.8] shows, in schematic view, in cross-section, an example of padding obtained at using the method illustrated in figures 6 and 7.

[0052] [Fig.9] is a schematic perspective view of a motor vehicle seat, for example. Description of the implementation methods

[0053] The drawings and description below contain, essentially, elements of a definite nature. They may therefore not only serve to better understand this disclosure, but also contribute to its definition, if necessary.

[0054] In the various figures, the same reference numerals designate identical or similar elements. For the sake of brevity, only the elements that are useful for understanding the described embodiment are shown in the figures and are described in detail below.

[0055] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "rear", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "lower", etc., or to orientation qualifiers, such as "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures or of a vehicle seat element or of a vehicle seat in its normal position of use.

[0056] In particular, the longitudinal direction X refers to the longitudinal direction of the seat. The longitudinal direction of the seat is considered to be the same as the longitudinal direction of the motor vehicle in which the seat is mounted. This longitudinal direction X corresponds to the normal direction of travel of the vehicle. The longitudinal direction X is horizontal. The transverse direction Y of the seat thus corresponds to the transverse or lateral direction of the motor vehicle. This transverse direction is perpendicular to the normal direction of travel of the vehicle. The transverse direction Y is horizontal. Finally, the vertical direction Z is a vertical direction of the seat, perpendicular to the longitudinal and transverse directions.

[0057] Reference is now made to figures 1 and 2 representing an example of the installation and implementation of a continuous process for manufacturing a mattress 10 on installation 1.

[0058] The process comprises extruding a thermoplastic polymer P, for example in the form of granules, through an extrusion die 2 of the installation 1. The extrusion die 2 includes extrusion nozzles 5, more clearly visible in the example of [Fig. 3], distributed along a lengthwise direction L1 and a widthwise direction L2 of the extrusion die 2. The extrusion die 2, starting from the thermoplastic polymer P, generates a curtain 3 of continuous fused fibers 4, falling by gravity. The curtain 3 of continuous fused fibers 4 then passes between two counter-rotating guide members 6, generating a 3D entanglement 7 of irregularly arranged fibers with loop fusion between the continuous fibers and along a layer of total thickness determined by the center distance dl between said two counter-rotating guide members 6.

[0059] The counter-rotating guide members 6 are arranged relative to each other and relative to the extrusion die 2 such that the generated 3D entanglement 7 has, on a first thickness ei extending from a first face 8, a first fiber density, and, on a second thickness e2 extending from a second face 9 opposite to the first face 8, a second fiber density greater than said first fiber density.

[0060] Finally, the 3D entanglement 7 of fibers is solidified by immersion in a coolant liquid B to form the padding 10.

[0061] The arrows on [Fig.1] illustrate the path followed by the fibers from extrusion to solidification.

[0062] The process makes it possible to obtain a padding 10 with a second face 9 having a higher density than the first face 8, forming a denser and more rigid shell, while the rest of the padding 10 including the first face 8 remains flexible. An example of such a padding 10 is illustrated in [Fig. 4].

[0063] The extrusion nozzles 5 are preferably distributed regularly along the lengthwise direction L1 of the extrusion die, and also along the widthwise direction L2. The extrusion temperature implemented in the extrusion die 2 is typically between 180°C and 240°C.

[0064] The curtain 3 in the illustrated example comprises a plurality of rows 11 of continuous fused fibers 4, each row 11 extending along the direction L1 in length of the extrusion die 2. The rows 11 are arranged side-by-side along the direction L2 in width of the extrusion die 2. The rows 11 comprise two end rows 1a and 11b, opposite, each having only one adjacent row.

[0065] In the illustrated example, the method comprises receiving the curtain 3 of continuous fused fibers 4 falling by gravity, for a first part 12 of the rows 11 of the curtain 3, between the two counter-rotating guide members 6 so as to generate said first fiber density. The first fiber density can be said to be a normal density, the fibers not having contact with the counter-rotating guide members 6 and freely forming the 3D entanglement 7 over the thickness eb

[0066] Furthermore, the method includes receiving the curtain 3 of continuous fused fibers 4 falling by gravity, for a second portion 13 of the rows 11 of the curtain 3, onto one of said two counter-rotating guide members so as to generate said second fiber density. The second portion 13 of the rows 11 of the curtain 3 comprises one of the two end rows 1a and 11b and optionally at least one adjacent row starting from the end row 1a or 11b. In this example, the second portion of the rows 11 of the curtain 3 comprises the end row lia and several, in this example two, adjacent rows 11 starting from the end row lia.

[0067] The fact that at least one row, in this example three rows 11, is received on one of the counter-rotating guide members 6 and not between the counter-rotating guide members 6, causes its displacement towards an adjacent row, as illustrated by the inclined arrow in [Fig. 2], at the moment when the 3D entanglement 7 is generated, and in particular before passing between the counter-rotating guide members 6 and before solidification. Thus, the fiber density in the area containing these rows combined by displacement from one to another, within the 3D entanglement 7, is increased compared to the rest of the 3D entanglement 7. This makes it possible to obtain the crust having the second density, which extends from the second face 9 and over the second thickness e2. In the illustrated example, the second thickness e2 is, for example, between 3 mm and 15 mm, in particular between 5 mm and 10 mm.

[0068] The two counter-rotating guide members 6 are driven in rotation at a speed, typically lower than the falling speed of the fibers, ensuring an accumulation of fibers which leads to the formation of loops which heat-weld between fibers, generating the irregular three-dimensional entanglement.

[0069] The two counter-rotating guide members 6 each comprise a roller, which is a cylindrical roller 16 in this example. It is one of the two cylindrical rollers 16, which receives the second part 13 of the rows 11 of the curtain 3. In the example illustrated in Figures 1 and 2, the two counter-rotating guide members 6 form two conveyors, each comprising, in addition to the cylindrical roller 16, a lower roller 17 located below said cylindrical roller 16, at a non-zero distance from it, as well as a belt 18 surrounding and connecting the cylindrical roller 16 and the lower roller 17 and forming the contour of the conveyor. The conveyors are advantageously arranged parallel to each other. The belt 18 of each conveyor is preferably permeable to the coolant B, so as to allow the passage of the coolant B through the belt 18. The belt 18 is, for example, made of chainmail.

[0070] The cylindrical rollers 16 are partially immersed in the coolant B, which may be water, to a height h less than or equal to half the total height of the cylindrical rollers, in this example substantially equal to half the total height ht of the cylindrical rollers 16. The total height ht denotes the diameter of the cylindrical rollers 16, as illustrated in [Fig. 1]. The cylindrical rollers 16 are advantageously identical to each other and of the same diameter. Thus, the contact between the second part 13 of the rows 11 of the curtain 3 of continuous fused fibers 4 and only one of said two counter-rotating guide members 6 takes place outside the coolant B.

[0071] In an unillustrated variant, the cylindrical rollers 16 may not be immersed in a coolant.

[0072] No receiving element for the continuous fused fibers 4 of the curtain 3 is arranged between the extrusion die 2 and the counter-rotating guide members 6. For example, no pallet is arranged on the path of the continuous fused fibers 4 between the extrusion die 2 and the counter-rotating guide members 6.

[0073] The method may include adjusting the center distance dl between the counter-rotating guide members 6 so that the center distance dl is less than the width w of the curtain 3 as it exits the extrusion die 2, along the direction L2. Such an adjustment may consist of bringing at least one of the counter-rotating guide members 6 closer to the other. In the illustrated example, the initial center distance may be such that the curtain 3 falls between the counter-rotating guide members 6. The adjustment then made may consist of moving the guide member 6, named 6a, located on the side of the end row 1la, to bring it closer to the other guide member 6, named 6b, so that at least the end row 1la is received on this guide member 6 that is being moved, i.e., on the guide member 6a.

[0074] Figure 3 shows another example of an installation 100 for implementing the process thus described. The example illustrated in Figure 3 differs from that of Figures 1 and 2 in that the counter-rotating guide elements 6 only include the cylindrical rollers 16, and therefore do not form conveyors in this example.

[0075] In the example illustrated in [Fig.3], we also visualize the 3D entanglement 7 of fibers, in continuous scrolling, which is then guided out of the coolant reservoir B to be dried, typically by shaking / vibrations.

[0076] In the example illustrated in [Fig. 3], the solidified 3D tangle 7b is directed towards a plurality of guide rollers before cutting to form the mattress 10. The moving layer is then cut, notably by cross-sections, allowing the production of different mattresses 10, as seen in [Fig. 3]. An abrasive treatment or thermoforming can be applied to round the edges, for example, or if a 3D shape is desired.

[0077] An example of a padding 10 obtained by implementing the process is illustrated in [Fig. 4]. The padding 10 comprises the 3D interlocking 7 after solidification, exhibiting, on a first layer extending from a first face 8, a first fiber density, and, on a second layer extending from a second face 9 opposite the first face 8, a second fiber density greater than the first fiber density. The padding 10 thus has a crust on the side of the second face 9, denser and harder than the rest of the padding extending over the first layer.

[0078] Such padding can be used in a motor vehicle seat component, in particular a seat or a backrest.

[0079] An example of a motor vehicle seat 100 has been illustrated in [Fig. 5]. It comprises a seat and a backrest forming a vehicle seat element 50 comprising a frame 51, or structure, in particular metallic, and the padding 10.

[0080] On [Fig.5], an XYZ reference frame is illustrated, the X direction oriented along the sliding direction of the slide G between the seat frame 51 and a floor of the vehicle, the Y direction oriented along a transverse direction of the seat, and the Z direction along the vertical.

[0081] The frame 51 comprises a seat frame 52 and a backrest frame 53, articulated around a transverse axis of rotation, for example by means of continuous type joints.

[0082] The padding 10 used for the vehicle seat element 50 is arranged so that the second face 9 is on the side of the frame 51, whether for the seat or the backrest in this example. In another example, only the seat may have padding 10 made according to the process described above. This allows, thanks to the second density of the layer formed on the second face 9, the elimination of the need for reinforcing fabric between the padding 10 and the frame 51. Indeed, the layer thus formed is sufficiently rigid and allows for the formation of a part intrinsic reinforcement of the padding. The number of constituent parts of the seat element is then reduced.

[0083] Another example of installation 1 and method is shown in Figures 6 and 7. This example differs from that of Figures 1 and 2 in that it is the guiding member 6b which has been brought closer to the guiding member 6a.

[0084] In this example, the second part 13 of the rows 11 which will fall until it comes into contact with the guide member 6b comprises a single row 11 of the curtain, namely the end row 11b.

[0085] We obtain the padding 10, illustrated in [Fig.4], with the second thickness e2 which is relatively small, being for example between 1 mm and 5 mm, in particular between 3 mm and 5 mm.

[0086] In this case, for example, the vehicle seat element 100, as illustrated in [Fig. 9], incorporates padding 10 with the second face 9 arranged to be in contact with a user or with a headrest. Indeed, the layer formed on the second face 9 remains relatively flexible and thin, increasing the density of the padding 10 only at the surface without imparting excessive rigidity. A headrest may or may not be added.

[0087] The rollers forming all or part of the counter-rotating guide elements 6 may alternatively be stepped or stepped cylindrical rollers, or may form a cam system. In this case, what applies to cylindrical rollers 16 and is described above or below may also apply to stepped or stepped cylindrical rollers, or to cam systems. The use of such rollers can create a relief on the padding during the shaping between the rollers of the 3D interlock.

[0088] The fibers can be hollow and / or solid. The fibers can have a diameter between 0.2 mm and 2 mm, preferably between 0.3 mm and 1.5 mm. The term "continuous" in "continuous fibers" means that the fibers are much longer than their diameter, and due to the process, typically by a ratio of at least 100, or even 500, or even 1000.

[0089] The fibers comprise a thermoplastic polymer, the fiber composition preferably comprising at least 95% by weight of PET. For example, the fiber composition, or even the padding composition, comprises 95% to 99% by weight of a first polymer from the polyester family such as PET (polyethylene terephthalate) and 1% to 5% by weight of a second polymer from the polyester family such as PTT (trimethylene terephthalate) or PBT (polybutylene terephthalate). The sum of PET and PTT (or PBT) can amount to 100% by weight of the fibers, or even the padding. The 3D interlocking of the padding 10 can have an apparent density of between 45 kg / m³ and 65 kg / m³.

[0090] Preferably, the voids between the fibers of the 3D fiber entanglement of the padding 10 are left free. This results in a highly breathable padding, due to the numerous inter-spaces between the fibers which promote air circulation.

Claims

Demands

1. A continuous method for manufacturing a mattress (10) comprising: - extruding a thermoplastic polymer (P) through an extrusion die (2) comprising extrusion nozzles (5) distributed along a longitudinal direction (L1) and a widthwise direction (L2) of the extrusion die (2), generating a curtain (3) of continuous fused fibers (4), falling by gravity, - passing said curtain (3) of continuous fused fibers (4) between two counter-rotating guide members (6), generating a 3D entanglement (7) of irregularly arranged fibers with loop fusion between the continuous fibers and in a layer of total thickness (Δt) determined by the center distance (Δt) between said two counter-rotating guide members (6), the counter-rotating guide members (6) being arranged relative to each other and relative to the extrusion die (2) such that the 3D entanglement (7) generated present,on a first layer (e1) extending from a first face (8), a first fiber density, and, on a second layer (e2) extending from a second face (9) opposite the first face (8), a second fiber density greater than said first fiber density, - solidification of the 3D entanglement (7) of fibers by immersion in a cooling liquid (B) to form the padding (10).

2. A method according to claim 1, wherein the curtain (3) comprises a plurality of rows (11) of continuous fused fibers (4), each row (11) extending along the longitudinal direction of the extrusion die, the rows (11) being arranged side-by-side along the width-to-width direction (L2) of the extrusion die (2) and comprising two end rows (1a, 11b), the method comprising receiving the curtain (3) of continuous fused fibers (4) falling by gravity: between said two counter-rotating guide members (6) for a first part (12) of the rows (11) of said curtain (3) so as to generate said first fiber density and - on only one of said two counter-rotating guide members (6) for a second part (13) of the rows (11) of said curtain (3) comprising one of the two end rows (1la; 11b) and possibly at least one row (11) adjacent from said end row (1la; 11b) so as to generate said second fiber density.

3. Method according to the preceding claim, wherein said second part (13) of the rows (11) comprises a single row (11) of said curtain (3), namely said one of the two end rows (1a; 11b).

4. Method according to claim 2, wherein said second part (13) of the rows (11) comprises several rows (11) of said curtain (3), in particular between two and four rows (11), namely said one of the two end rows (1a; 11b) and at least one, in particular between one and three, rows (11) adjacent from said one of the two end rows (1a; 11b).

5. A method according to any one of claims 1 to 4, wherein said two counter-rotating guide members (6) each comprise a roller, in particular (16) or stepped or cylindrical stepped or a cam system.

6. A method according to the preceding claim, wherein said two counter-rotating guide members (6) form two conveyors each comprising, in addition to said roller, a lower roller (17) located below said roller, at a non-zero distance from it, and a belt (18) surrounding and connecting said roller and said lower roller (17).

7. A method according to one of the two preceding claims, wherein said rollers (16) are partially immersed in the coolant over a height (h) less than or equal to half the total height (ht) of said rollers (16).

8. A method according to any one of the preceding claims, comprising an adjustment of the center distance (dl) between said counter-rotating guide members (6), so that said center distance (dl) is less than the width (w) of the curtain (3) at the exit of the extrusion die (2).

9. Motor vehicle seat element (50) comprising a secure mattress (10) obtained using the method according to any one of the preceding claims.

10. Seat element (50) according to the preceding claim, comprising a frame (51), in which said second face (9) is disposed on the side of the frame (51), said second fiber density being in particular between two and four times said first fiber density.

11. Seat element (50) according to claim 9, wherein said second face (9) is arranged to be in contact with a user or with a headgear, said second fibre density being in particular about twice said first fibre density.

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