PROCESS FOR PRODUCING MOTOR VEHICLE SEAT CUSHIONING

Abstract

The invention relates to a method for creating a motor vehicle seat cushion. The inventive method provides for a cover having a format of a complex comprising a layer of covering material and a sublayer of elastically compressible foam, and for arranging on the sublayer a film based on thermoplastic polyurethane. The film has a melting point and a melt mass-flow index that breaks down under the action of the heat released during the formation of the foam. The film is provided with a reinforcing thin-film to form a two-layer barrier against the penetration of foam. The reinforcing thin-film is based on a thermoplastic polyurethane with a melting point higher than that of the film and has a melt mass-flow index lower than that of the film, to have greater strength than the film so that the reinforcing thin-film breakdown under the action of heat is delayed.

Claims

1. A method of making a cushion for a motor vehicle seat, the method comprising: providing a cover having a format of a complex comprising a layer of covering material and a sublayer of elastically compressible foam, setting the format in place within a mould defining a moulding cavity, the covering layer being disposed against the wall of the moulding cavity, arranging a film based on thermoplastic polyurethane over the sublayer, injecting an elastically compressible foam precursor mixture into the moulding cavity, making a padding block, the film having a melting point and a melt mass-flow index that breaks down when subjected to the heat released during the formation of the foam of the block, enabling overmoulding of the sublayer by the block without substantial penetration of the foam of the block into the thickness of the sublayer, after expanding the foam, demoulding the obtained cushion, the method wherein the film is provided with a reinforcing sheet directed towards the cavity, to form a two-layer barrier against the penetration of foam, the sheet being based on thermoplastic polyurethane with a melting point higher than that of the film and with a melt mass-flow index lower than that of the film, to have an increased resistance in comparison with the film in order to be broken down with a delay under the action of the heat released during the formation of the foam of the block.

2. The method according to claim 1, wherein: the film has a melting point between 45° C. and 52° C. and a melt mass-flow index between 17 g/10 min and 26 g/10 min, and the sheet has a melting point comprised between 53° C. and 60° C. and a melt mass-flow index comprised between 6 g/10 min and 16 g/10 min.

3. The method according to claim 2, wherein: the film has a melting point between 48° C. and 52° C. and a melt mass-flow index comprised between 22 g/10 min and 26 g/10 min, and the sheet has a melting point between 53° C. and 57° C. and a melt mass-flow index comprised between 12 g/10 min and 16 g/10 min.

4. The method according to claim 1, wherein each of the film and the sheet has a thickness comprised between 7 microns and 20 microns.

5. The method according to claim 1, wherein the foam sublayer has a density of 0.028±0.002.

6. A cushion for a motor vehicle seat made by a method according to claim 1, the cushion comprising: a cover having a first format, the format comprising a layer of a covering material and a sublayer of an elastically compressible foam, in particular polyurethane based, a padding block made of an elastically compressible foam, the block overmoulding the format while leaving the sublayer substantially free of foam into the thickness thereof.

7. A motor vehicle seat comprising a cushion according to claim 6, the cushion being associated, by the periphery of the cover, to a framework of the seat.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Further features and advantages of the invention will come out in the following description, made with reference to the appended figures, wherein:

[0034] FIG. 1 is a schematic partial sectional view of a cushion during manufacture according to one embodiment, the foam precursor mixture having just been injected in the mould,

[0035] FIG. 2 is a schematic partial sectional view of the cushion of FIG. 1 once completed.

DETAILED DESCRIPTION

[0036] Referring to the figures, there is described a method for making a cushion 1 of a motor vehicle seat, the method comprising the following steps: [0037] providing a cover comprising a format 2 of a complex comprising a layer of a covering material 3 and a sublayer 4 of an elastically compressible foam, [0038] setting the format in place within a mould 5 defining a moulding cavity 6, the covering layer being disposed against the wall 7 of the cavity, [0039] disposing a film 8 based on thermoplastic polyurethane over the sublayer, [0040] injecting an elastically compressible foam precursor mixture 9 into the cavity, to make a padding block 10, the film having a melting point and a melt mass-flow index such that it breaks down under the action of heat released during the formation of the foam of the block, in order to enable overmoulding of the sublayer by the block substantially without penetration of the foam of the block into the thickness of the sublayer, [0041] after expanding the foam, demoulding the obtained cushion 1,

[0042] the film is provided with a reinforcing sheet 11 directed towards the cavity, to form a two-layer barrier against the penetration of foam, the sheet being based on thermoplastic polyurethane with a melting point higher than that of the film and with a melt mass-flow index lower than that of the film, to have an increased resistance in comparison with the film in order to be broken down with a delay under the action of the heat.

[0043] In particular, the melt mass-flow index are measured according to the standard NF T 51-016 in force on the application filing date, at 190° C. with a forced-flow capillary rheometer whose piston is loaded with a 2.160 kg mass.

[0044] In particular, the melting points are measured through a differential scanning calorimetry (DSC), according to the standard ISO 11357 in force on the application filing date.

[0045] According to one embodiment: [0046] the film 8 has a melting point comprised between 45 and 52° C. and a melt mass-flow index comprised between 17 and 26 g/10 min, [0047] the sheet 11 has a melting point comprised between 53 and 60° C. and a melt mass-flow index comprised between 6 and 16 g/10 min.

[0048] More particularly, according to one embodiment: [0049] the film 8 has a melting point comprised between 48 and 52° C. and a melt mass-flow index comprised between 22 and 26 g/10 min, [0050] the sheet 11 has a melting point comprised between 53 and 57° C. and a melt mass-flow index comprised between 12 and 16 g/10 min.

[0051] Many tests have enabled the Applicant to observe excellent results with a film 8 and a sheet 11 having such characteristics.

[0052] According to one embodiment, each of the film 8 and the sheet 11 has a thickness comprised between 7 and 20 microns.

[0053] According to one embodiment, the polyol used to make the film 8 is polyester based.

[0054] According to one embodiment, the polyol used to make the sheet 11 is polyester based.

[0055] According to one embodiment, the isocyanate used to make the film 8 comprises an aromatic group.

[0056] According to one embodiment, the isocyanate used to make the sheet 11 comprises an aromatic group.

[0057] According to one embodiment, the foam sublayer 4 has a density of 0.028±0.002, which usually corresponds to a poor quality of the foam used for covers associated to a padding block by draping and not by overmoulding the cover by the block.

[0058] The use of such a low-cost sublayer 4 allows making a cushion 1 with a reduced cost.

[0059] The use of such a sublayer 4 is made possible by the use of the film 8 provided with the sheet 11 as described hereinabove.

[0060] According to one embodiment, the foam sublayer 4 is polyurethane based.

[0061] According to one embodiment, the foam sublayer 4 has a thickness comprised between 1.5 and 2 mm.

[0062] According to the represented embodiment, the foam sublayer 4 is provided, on its outer face, with a protective cloth 12, in particular with a rectangular or circular mesh pattern.

[0063] According to a represented embodiment, the cover comprises a second format associated edge-to-edge, in particular by sewing, to the first format 2, the second format not being overmoulded by the padding block 10.

[0064] According to one embodiment, the second format is located at the lateral portion of the cushion 1, its dissociation from the padding block 10 allowing for a better strength of the block with regards to the bending it undergoes when passengers get in/out of the vehicle.

[0065] According to one embodiment, the foam of the block 10 has a different density depending on whether it is located opposite the first 2 or second format, the foam having in particular an increased density at the lateral portions of the cushion 1, to enable a firm lateral support of the passenger.

[0066] There is now described a cushion 1 for a motor vehicle seat made by such a method, the cushion comprising: [0067] a cover comprising a first format 2, the format comprising a layer of a covering material 3 and a sublayer of an elastically compressible foam 4, in particular polyurethane based, [0068] a padding block 10 made of an elastically compressible foam, the block overmoulding the format while leaving the sublayer substantially free of foam into the thickness thereof.

[0069] Finally, a non-represented motor vehicle seat is described, comprising such a cushion 1, the cushion being associated, by the periphery of the cover, to a framework of the seat.

[0070] In order to achieve the association of the cushion 1 on the seat framework, profiles are particularly used attached, for example by sewing, at the periphery of the cover, the profiles nesting into anchor portions provided on the framework.