Vehicle seat element, especially backrest of a vehicle seat, and method for manufacturing the same

Abstract

A vehicle seat element (13; 16; 34) comprises a frame (14; 17; 35) and a trimming (15; 18; 36) fixed to the frame (14; 17; 35). The trimming (15; 18; 36) comprises a padding. The padding comprises a mat (56) of an entanglement of thermoplastic fibers forming loops welded together, the fibers being made of a material including a polymer. The mat (56) comprises a first portion (56a) extending on a first face (17A) of the frame (17), and a first and a second tabs (561; 562) extending on a second face (17B) of the frame (17). An overlapping portion of the first tab (561) overlaps an overlapped portion of the second tab (562) on the second face (17B) of the frame (17). The overlapping portion of the first tab (561) and the overlapped portion of the second tab (562) are fixed together.

Description

Vehicle seat element, especially backrest of a vehicle seat, and method for manufacturing the sameTechnical Field

[0001] The present disclosure relates to a vehicle seat element for vehicle, especially an automotive, and to a method for manufacturing the same. The vehicle seat element can especially be a backrest of a seat.Prior art

[0002] A vehicle seat element, especially a backrest or a cushion of a vehicle seat, usually comprises a frame and a trimming, fixed on the frame. The trimming includes at least a padding, which can be fixed on a support part. The padding usually comprises one or more blocks of urethane polymer foam (or polyurethane, PU), in particular polyurethane foam obtained from polyester / polyol (or PUR) type polyols. Such blocks can be produced and shaped in molds. These blocks of urethan polymer foam can even be overmolded over the frame or the support part for the padding. Thus, these blocks of foam can easily be adapted to different forms of a vehicle seat element. Moreover, these blocks can easily be fixed into the vehicle seat element.

[0003] A polyurethane foam padding is satisfactory, but can retain moisture, especially in humid conditions. This may cause a feeling of discomfort for an occupant of the vehicle seat, an element of which includes such padding.

[0004] In addition, polyurethane foam is conventionally made by mixing, among other things, polyols with isocyanates. The chemical reaction implemented emits CO2 to form a foam. The CO2 emitted contribute to global warming.

[0005] Furthermore, polyurethane foam is not recyclable.

[0006] Thus, it appears desirable to limit the use of polyurethane in the padding of trim elements of a vehicle.

[0007] French patent application FR-A-3139025 teaches a padding for a vehicle seat element, formed from a 3D entanglement of continuous fibers, arranged irregularly and forming loops welded together. This padding is breathable and requires less CO2 to manufacture. However, this entanglement of continuous fibers cannot be fixed in a vehicle seat element using the same fixation system than those used for a padding made in a polyurethan foam.Summary

[0008] In the present disclosure, a vehicle seat element is described, especially a backrest of a vehicle seat, comprising a frame and a trimming directly or indirectly fixed to the frame, the trimming comprising a padding, the padding comprising, preferably consisting in, a mat of an entanglement of thermoplastic fibers forming loops welded together, the fibers being made of a material including a polymer, the mat comprising at least one first portion extending on a first face of the frame, destined to be oriented toward an occupant of the vehicle seat, and a first and a second tabs extending at least partially on a second face of the frame, opposed to the first face of the frame, wherein at leastone overlapping portion of the first tab overlaps at least one overlapped portion of the second tab on the second face of the frame and wherein the overlapping portion of the first tab and the overlapped portion of the second tab are fixed together.

[0009] Optionally, the vehicle seat element can comprise one or more of the following features, taken alone or in combination:- the overlapping portion of the first tab and the overlapped portion of the second tab are fixed together by ultrasonic welding;- the overlapping portion of the first tab and the overlapped portion of the second tab are fixed together along a fixing portion, said fixing portion comprising separate strips, preferably with enlarged extremities;- the overlapping portion of the first tab and the overlapped portion of the second tab are fixed together along a fixing portion, wherein the fixing portion is flush with the first and second tabs, outside of the overlapping portion of the first tab and the overlapped portion of the second tab, on its face oriented opposite to the frame;- the trimming includes a padding support fixed onto the frame, the mat being fixed around at least one end of the padding support;- the padding support comprises a portion extending on the first face of the frame and a portion extending on the second face of the frame;- the padding support extends in a U-shape around an extremity of the frame; and- the vehicle seat element is one among:- a backrest of a vehicle seat;- a cushion of a vehicle seat;- a headrest of a vehicle seat;- an armrest.

[0010] According to another aspect, it is described a method for manufacturing a vehicle seat element according to any one of the preceding claims, comprising the steps of:- providing the frame of the vehicle seat element and the mat of the trimming;- folding the mat of the trimming so that at least one first portion extends on a first face of the frame, destined to be oriented toward an occupant of the vehicle seat, and a first and a second tabs extend at least partially on a second face of the frame, opposed to the first face of the frame, wherein at least one overlapping portion of the first tab overlaps at least one overlapped portion of the second tab on the second face of the frame; and- fixing together the at least one overlapping portion of the first tab with the at least one overlapped portion of the second tab.

[0011] The overlapping portion of the first tab and the overlapped portion of the second tab can be fixed together by ultrasonic welding.Brief description of the drawings

[0012] The detailed description particularly refers to the accompanying figures in which:

[0013] Fig. 1 schematically shows an example of a vehicle seat in a section view;

[0014] Fig. 2 is a flowchart of an exemplary method of manufacturing the vehicle seat backrest of Fig. 1 ;

[0015] Fig. 3 schematically shows the backrest frame of the vehicle seat of Fig. 1 ;

[0016] Fig. 4 schematically illustrates a step of the method of Fig. 2;

[0017] Fig. 5 schematically illustrates the back side of a padding support of the backrest of the vehicle seat of Fig. 1 ;

[0018] Fig. 6 schematically illustrates a padding to be fixed onto the padding support of Fig. 5;

[0019] Fig. 7 schematically shows a portion of the backside of the padding support of Fig. 5 on which the padding of Fig. 6 is placed;

[0020] Fig. 8 schematically shows a cross-section of a detail of the padding of Fig. 6 placed on the padding support of Fig. 5;

[0021] Fig. 9 schematically illustrates a step of fixing the padding of Fig. 6 onto the padding support of Fig. 5 by ultrasonic welding;

[0022] Fig. 10 schematically illustrates the padding of Fig. 6 fixed onto the padding support of Fig. 5;

[0023] Fig. 11 schematically illustrates a detail of Fig. 10 in cross-section.Detailed description

[0024] In the various figures, the same references designate identical or similar elements. For brevity, only those elements which are useful to understanding the embodiment described are shown in the figures and described in detail below.

[0025] 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 qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as "horizontal", "vertical", etc., unless otherwise specified, these are in reference to the orientation of the figures or of a vehicle seat in its normal position of use.

[0026] 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 corresponds to a direction 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.

[0027] Fig. 1 schematically shows a motor vehicle seat 10 mounted on a slide mechanism 12.

[0028] The seat 10 includes a cushion 13 (or seating portion), with a cushion frame 14 and a cushion trimming 15, on which is mounted a backrest 16, with a backrest frame 17 and a backrest trimming 18. Here the backrest frame 17 pivots about an axis A, relative to the seating portion frame 14. To do so, a hinge mechanism 20 is arranged between the seating portion frame 14 and the backrest frame 17. The axis A is for example substantially parallel to the transverse direction Y.

[0029] The seating portion 13 is mounted on movable profiles 22, also called sliders or male profiles, by means of feet 24, 26. Each movable profile 22 is part of a slide 12 and is associated with a fixed profile 28. The fixed profile 28 is also called a rail or female profile. The fixed profile 28 is fixed to the floor 30 of a motor vehicle.

[0030] In this example, the seat 10 comprises a manual control member 32, called a lever, for controlling the sliding of the slides 12. This manual control member 32 makes it possible in particular to lock and unlock the stop systems which prevent the sliding of the movable profiles 22 relative to the respective fixed profiles 28. Once the stop systems are released, the manual control member 32 can also be used to slide the movable profiles 22 relative to their respective fixed profiles 28 of the slide 12 along the longitudinal direction X of the slides 12. The fixed 28 and movable profiles 22 of the slides 12 may be of metal.

[0031] Alternatively, the movement of the movable profiles 22 relative to the fixed profiles 28 is controlled by means of an actuator. One or more actuator control buttons may then be provided on the seat 10, in particular on the seating portion 13.

[0032] The seat 10 further comprises a headrest 34. The headrest 34 comprises a headrest frame 35 and a headrest trimming 36. The headrest frame 35 is connected to the backrest frame 17 by means of at least one headrest attachment rod 38, preferably two headrest attachment rods 38 received in sockets formed by the backrest frame 17. The headrest attachment rod(s) 38 may be of variable length to allow adjusting the positional height of the headrest 34. Additionally or alternatively, the headrest frame 35 is movable relative to the headrest attachment rod(s) 38 to allow this adjusting of the positional height of the headrest 34. The headrest trimming 36 and / or the backrest trimming 18 may cover all or part of the headrest attachment rod(s) 38, for example to improve the aesthetics of the vehicle seat 10.

[0033] In the following, the backrest 16 of the vehicle seat 10 and its method of manufacturing 100 illustrated in Fig. 2 will be described in more detail.

[0034] As illustrated in Fig. 2, the method 100 comprises a first step 102 of providing a backrest frame 17. As illustrated in Fig. 3, the backrest frame 17 essentially comprises a first upright 17i, a second upright 172, a first crossmember 17s, hereinafter called "lower crossmember 173", and a second crossmember 174, hereinafter called "upper cross member 174". The uprights 17i, 172 and the crossmembers 17s, 174 form a backrest frame 17 in the form of a framework. To achieve this, the uprights 17i, 172, and the crossmembers 17s, 174 can be fixed together, in particular welded together. Alternatively, the backrest frame 17 is one piece, being for example molded.

[0035] Here, the headrest attachment rods 38 are already fixed on the upper crossmember 174 of the backrest frame 17 at this first step 102. Alternatively, however, these headrest attachment rods 38 may be attached to the upper crossmember 174 of the backrest frame 17 in a later step.

[0036] During a second step 104 of the manufacturing method 100, a first side trimming module 40 and a second side trimming module 42 are fixed to the front face 17A of the backrest frame 17, visible in Fig. 3, on a respective upright 17i, 172 of the backrest frame 17. Thus, a side trimming module 40, 42 is arranged on each side of the backrest frame 17. The front face 17A of the backrest frame 17 is the face of the backrest frame 17 intended to be oriented towards an occupant of the vehicle seat 10. The rear face 17B of the backrest frame 17 is the face opposite to the front face 17A.

[0037] In the present case, the first and second trimming modules 40, 42 form a bolster on each side of the backrest 16.

[0038] Each side trimming module 40, 42 here comprises padding each padding being fixed on a respective support 48, 50. Each support 48, 50 may be fixed to the respective upright 17i, 172 of the backrest frame 17 by snap fitting and / or welding and / or screwing and / or riveting and / or forcibly inserting a contoured relief into a complementary relief, in particular. Here, each support 48, 50 can comprise a respective upright with snap fitting reliefs 52 making it possible to fix on the upright, here by snap fitting, an airbag support to which an airbag is fixed. Each airbag is connected to a pump for inflation. The airbags thus improve the lateral support for the occupant of the vehicle seat 10. In the example illustrated, each snap fitting relief 52 takes the form of a U-shaped hook, into which is snap fitted a rod formed by the inflatable cushion support. Other shapes of the snap fitting reliefs 52 are accessible to those skilled in the art.

[0039] The first side trimming module 40 intended to be positioned centermost in the motor vehicle equipped with the seat 10, can further comprise a side airbag safety device. Such an airbag device aims to avoid direct head-to-head impacts between the occupants of two seats arranged transversely, one next to the other. The airbag system is at least partially covered by the padding of the first side upholstery module 40.

[0040] The method of manufacturing 100 then continues with a step 106 of fixing a padding support 54 onto the backrest frame 17, on the front face 17A. Here, the padding support 54 is disposed between the two side trimming modules 40, 42.

[0041] As illustrated on Fig. 4 and Fig. 5, the padding support 54 can be in the form of a plate.

[0042] The padding support 54 can comprise an upper portion 54i, a middle portion 542, and a lower portion 54s.

[0043] The upper portion 54i can be shaped to facilitate the installation of the padding support 54 on the backrest frame 17. To do so, the upper portion 54i of the padding support 54 can have openings suitable for sockets fixed to the backrest frame 17 and adapted to receive the headrest attachment rod(s) 38. Thus, the upper portion 54i is placed above the upper crossmember 174, around the sockets. The padding support 54 thus covers the upper crossmember 174 of the backrest frame 17. To do so, the upper portion 54i of the front central padding support 54 can be curved so as to forma housing 60 receiving the upper crossmember 174 of the backrest frame 17 as well as an upper portion of the first and second uprights 17i , 172. The housing 60 is delimited by the front wall of the padding support 54, extending on the front face of the backrest frame 17, and a backward curved edge 62 of the padding support 54, especially of its upper portion 54i, extending essentially on the rear face 17B of the backrest frame 17.

[0044] The inner faces of the upper portion 54i of the padding support 54 and of the backward curved edge 62, oriented towards the interior of the housing 60, can be provided with reliefs to guide the mounting of the padding support 54 on the backrest frame 17 and / or to participate to the fixation of the padding support 54 on the backrest frame 17. For example, the inner face of the upper portion541 of the padding support 54 and of the backward curved edge 62, oriented towards the interior of the housing 60, can be provided with snap fitting reliefs adapted to cooperate with complementary snap fitting reliefs provided on the backrest frame 17, in particular on the upper crossmember 174 and / or the uprights 17i, 172.

[0045] The middle portion 542 of the padding support 54 essentially has the function of supporting a backrest padding 56, where the occupant of the vehicle seat 10 primarily bears against the seat backrest 16. The middle portion 542 thus advantageously provides sufficient mechanical resistance so that the padding 56 does not sink in completely when an occupant of the vehicle seat 10 leans on the seat backrest 16. However, the middle portion 542 is advantageously still relatively flexible in order to ensure the comfort of the occupant of the vehicle seat 10. Deflection of the middle portion542 of the padding support 54 can be limited by reliefs on the backrest frame 17 and / or on a rear shell fixed on the rear face of the backrest frame 17B.

[0046] Finally, the lower portion 54s is shaped here to ensure the attachment of the padding support 54, in this case on the backrest frame 17. Here, this lower portion 54s is curved backwards and is provided with snap fitting reliefs 64 suitable for engaging with complementary reliefs on the lower crossmember 17s of the backrest frame 17 and / or on a rear shell fixed on the rear face of the backrest frame 17B.

[0047] The padding support 54, especially its middle portion 54s, can support one or more members 55 making it possible to fulfill one or more comfort and / or safety functions for the occupant of the vehicle seat 10. For example, a fan may be attached to this central part, suitable for blowing air towards the occupant of the seat. According to another examples, a vibrator and / or a pneumatic equipment for performing a massage function and / or a heating equipment can be fixed on the padding support 54.

[0048] The method of manufacturing 100 then continues with a step 108 of providing the backrest padding 56.

[0049] In the present case, the backrest padding 56 is comprised of a mat of a heap (or entanglement) of fibers, said fibers forming loops which are heat-sealed together. The backrest padding 56 has the form of a mat since its thickness is sensibly constant on its entire surface. The thickness is the least dimension of the backrest padding 56. The thickness of the backrest padding56 may be between 15 mm, preferably 50 mm, and 100 mm, preferably 60 mm. The thickness can be five times, preferably ten times least than the two other dimensions of the backrest padding 56 which are its length and its width. Preferably, the thickness of the backrest padding 56 is measured in a direction which is substantially perpendicular to the padding support 54.

[0050] The fibers in the heap of fibers forming the backrest padding 56 can be called “continuous” here in that their length is very much greater than their diameter. For example, the ratio between the length of the fibers and their diameter can be at least equal to 100, preferably 500, and more preferably 1000. Preferably, the fibers extend from a first end on a first edge of the heap, to a second end on a second edge of the heap, opposite the first edge. In addition, the diameter of the fibers can be between 0.2 mm and 2 mm, preferably between 0.3 mm and 1.5 mm. The fibers can be hollow fibers and / or solid fibers.

[0051] The heap of fibers can be described as “three-dimensional”, because the thickness of the heap of fibers obtained is not negligible, in that it is preferably much greater than the diameter of the fibers. The thickness of the heap of fibers obtained is in particular at least 10 times greater, preferably at least 30 times greater, more preferably at least 50 times greater, than the diameter of the fibers of the heap of fibers.

[0052] The fibers comprise a thermoplastic polymer, the composition of the fibers preferably comprising at least 95% by weight of PET. For example, the composition of the fibers, or even the cushion comprises:- 95% to 99% by weight of a first polymer of the polyester family such as PET (polyethylene terephthalate),- 1 % to 5% by weight of a second polymer of the family of polyesters, such as PTT (Polytrimethylene terephthalate) or PBT (polybutylene terephthalate).The sum of the PET and of the PTT (or PBT) can be 100% by weight of the fibers, or even of the backrest padding 56. The backrest padding 56 may have an apparent density of between 20 kg / m3and 70 kg / m3, or even between 45 kg / m3and 65 kg / m3.

[0053] Preferably, the voids between the fibers of the heap of fibers of the backrest padding 56 are left free. A very breathable backrest padding 56 is obtained, because of the numerous interspaces between the fibers that promote air circulation.

[0054] An example of a method for producing the backrest padding 56 is briefly described below.

[0055] The method which can be continuous, comprises a first step consisting of extruding a plastic material containing at least one thermoplastic polymer, in an extrusion die comprising a plurality of extrusion nozzles. To do this, the extrusion die can be supplied with polymer granules / s / . The extrusion die can for example be adapted to heat the plastic material, in particular the polymer granules / s / , to a temperature between 180°C and 240°C. The extrusion nozzles can be regularly distributed in two perpendicular directions to form a matrix of extrusion nozzles. The extrusion die thus makes it possible to form a curtain of continuous, melted fibers, the density of fibers of which is substantially constant in cross section (that is to say in a plane perpendicular to the direction ofadvancement of the extruded fibers). The extrusion nozzles can be distributed in a horizontal plane. Also, to keep the density of the fibers substantially constant in cross section of the curtain of fibers, the fibers are here driven by gravity at the exit of the extrusion die. By “curtain of fibers”, it is meant here a configuration of the fibers extending substantially parallel to each other, the fibers being included, in a plane perpendicular to their direction of advancement, in an envelope curve corresponding substantially to the section of the extrusion die, for example substantially rectangular.

[0056] In a second step of the method, the molten fibers are driven towards two counter-rotating guide members. The guide members cab be identical rollers, in particular of the same, constant diameter. Preferably, the minimum distance between the two rollers is less than the smallest dimension (or width) of the cross section of the curtain of fibers, while the other dimension of the cross section of the curtain of fibers, the largest (or length), is substantially equal to or less than the length of the rollers. Preferably, at the outlet of the extrusion die and upstream of the rollers, the temperature of the plastic material from which the fibers are formed is greater than or equal to 150 °C, preferably greater than or equal to 160 °C, and / or less or equal to 190 °C, preferably less than or equal to 180 °C. Preferably, the two rollers rotate at the same speed. The speed of the two rollers is chosen so as to create a clogging of melted fibers upstream of the two rollers. This can in particular be achieved by choosing a speed of the rollers such that the product of the area of the smallest surface between the two rollers multiplied by the rotation speed of the rollers is less than the surface flow rate of the extrusion die. According to a particular example, this can in particular be obtained by choosing a rotation speed of the rollers, lower than the speed of the curtain of fibers upstream of the two rollers.

[0057] Thus, an accumulation of melted fibers forms upstream of the rollers. The fibers then tend to form continuous loops, which, due to the temperature of the fibers, weld together. In particular, fibers can fuse with each other.

[0058] A heap of molten fibers can thus be obtained, which is then guided between the rollers to have a substantially rectangular cross section. In particular, the thickness of the heap of fibers can be defined by the distance between the two rollers, the thickness of the heap of fibers being in particular substantially equal to the distance between the two rollers. The fibers cany be distributed irregularly in the tangle of fibers, in particular according to a distribution which may appear random to an observer. The volume of fibers crossing the area between the two rollers can be substantially constant per unit of time. In other words, the heap of fibers can be continuous at the exit from the rollers.

[0059] In a third step of the process, the fibers are solidified. To do this, the tangle of fibers can be guided into a cooling bath, for example a bath of cooling liquid such as water, after passing through the passage between the two rollers. For example, the two rollers can be submerged halfway.

[0060] In a fourth step of the process, the heap of fibers is guided, outside the cooling bath, in particular to be dried. Drying can be carried out by shaking / vibrating the heap of fibers. The heap of fibers can then be shaped, especially cut, to form the backrest padding 56 as illustrated on Fig. 6.

[0061] The backrest padding 56 can be substantially homogeneous, having similar fibers and a homogeneous apparent density, in substantially the entire volume of the backrest padding 56.

[0062] As can be seen on Fig. 6, the backrest padding 56 comprise a main portion 56a designed to extend on the front face 54A of the padding support 54, here between the two bolsters on the backrest 16, and fixing tabs 56i, 562 designed to extend at least partially on the rear face of the backrest frame 17B. As illustrated, the backrest padding 56 comprises one central fixing tab 56i, and two lateral fixing tabs 562 extending on each side of the central fixing tab 56i, as illustrated on Fig. 6, id est before to be fixed in the backrest 16.

[0063] The method of manufacturing 100 then continues with a step 110 of fixing the backrest padding 56 onto the backrest frame 17.

[0064] To do so, the main portion 56a of the backrest padding 56 is placed against the main portion 542 of the padding support 54, on the front face 54A of the padding support 54. Then, the fixing tabs 56i, 562 are folded so as to extend at least partially facing the rear side of the backrest frame 17B, as illustrated on Fig. 7. As it can be more clearly seen on Fig. 8, the fixing tabs 56i, 562 overlap each other on the rear side of the backrest frame 17B. More specifically, the central fixing tab 56i here comprises two overlapping portions each overlapping a corresponding overlapped portion of a lateral fixing tab 562.

[0065] In the present case, the fixing tabs 56i, 562 face the outer face of the backward curved edge 62 of the padding support 54, opposite to the housing 60. According to another embodiment, the tabs 56i, 562 could further face the inner face of the backward curved edge 62 of the padding support 54, oriented toward the housing 60, the fixing tabs 56i, 562 being then folded around the free end 62a of the backward curved edge 62 of the padding support 54.

[0066] The fixing tabs 56i, 562 then extend spaced apart from the backward curved edge 62 of the padding support 54 or in contact with the backward curved edge 62 of the padding support 54. Moreover, in the present case, the fixing tabs 56i, 562, when they are folded, form together with the main portion 56a of the backrest padding 56 corners around the padding support 54.

[0067] The overlapping portions of the fixing tabs 56i, 562 are then fixed together. Accordingly, the backrest padding 56 is fixed onto the padding support 54, the corners formed by the fixing tabs 56i, 562 and the main portion 56a of the backrest padding 56 preventing movements of the backrest padding 56 with regard to the padding support 54.

[0068] In the present case, the overlapping portion of the central fixing tab 56i and the overlapped portion of a lateral fixing tab 562 are fixed together by ultrasonic welding, as schematically illustrated on Fig. 9. To do so, an ultrasonic welding system 66 is used. Ultrasonic welding is preferred because it does not imply any third part or product to bind the fixing tabs 56i, 562 together. Further benefits of ultrasonic welding comprise that it is quick, can easily be automated, make clean and precise joints and the site of the weld is very clean.

[0069] As illustrated, the ultrasonic welding system 66 is composed of:- an electronic ultrasonic generator 68 delivering an electric signal;- a convertor 70 e.g. a piezoelectric transducer, to convert the electrical signal into a mechanical vibration using piezo electric effect;- an optional booster 72 to modify the amplitude of the vibration mechanically; and- a sonotrode 74 (or horn) to modify the amplitude mechanically and apply the mechanical vibration to the fixing tabs 56i, 562 to be welded.

[0070] The convertor 70, the booster 72, if any, and the sonotrode 74 form a stack. They are specifically tuned to resonate at the same ultrasonic frequency, e.g. 20 kHz, 30 kHz or 40 Khz.

[0071] A press 76 and an anvil 78 can also be associated with the ultrasonic welding system 66 to maintain the sonotrode 74 pressed against the upper one among the fixing tabs 56i, 562. The anvil 78 can also allow the high frequency vibrations to be directed to the interface between the fixing tabs 56i, 562 to be fixed together.

[0072] Thanks to the ultrasonic welding system 66, especially the sonotrode 74, low-amplitude high- frequency ultrasonic acoustic vibrations are locally applied to the overlapped portion of the lateral fixing tab 562 being held sandwiched with the overlapping portion of the central fixing tab 56i between the press 76 and the anvil 78. Absorption of the ultrasonic acoustic vibrations causes local melting and mixing of the thermoplastic of the fixing tabs 56i, 562 along a joint 80. In other words, the ultrasonic energy melts contact points between the overlapped portion of the lateral fixing tabs 562 and the overlapping portion of the central fixing tab 56i, creating a joint 80 by local fusion and / or mixing of the thermoplastic material of the fixing tabs 56i, 562.

[0073] The joint 80 between the fixing tabs 56i, 562 can have different designs. The shape of the sonotrode 74, especially, can influence the shape of the joint between the fixing tabs 56i, 562.

[0074] As can be seen in Fig. 10, the joint 80 can comprise several segments 82 (or strips) with enlarged extremities 84. The segments 82 of the joint 80 can be parallel. Such a form of the joint 80 allow an effective fixing of the fixing tabs 56i, 562 together while maintaining a satisfactory flexibility of the backrest padding 56. Flexibility of the backrest padding is preferred for comfort of the seat occupant as well as for esthetical installation of the backrest padding 56 on the padding support 54, especially on its backward curved edge 62.

[0075] As can be seen on Fig. 11 , the joint 80 is preferably flush with the fixing tabs 56i, 562 on their outside surfaces 56i°, 562°. The outside surfaces 56i°, 562° of the fixing tabs 56i, 562 are free, opposite to the inside surfaces 56i'; 562' facing and, in the present case, in contact with, the padding support 54. Since ultrasonic welding implies a melting of at least one of the fixing tabs 56i, 562, a void 83 can appear between the padding support 54 and the joint 80. It is preferred that this void 83 does not appear of the free face of the padding 56, but rather on the face of the padding in contact with the padding support 54 and / or facing the frame 17 of the backrest.

[0076] Above is described the fixation of the backrest padding 56 at the top of the padding support 54. The backrest padding 56 can be fixed the same way to the lower end of the padding support 54. In this case, the backrest padding 56 comprises fixing tabs at its lower end, opposite to its upper end from which the previously described fixing tabs 56i, 562 extend.

[0077] The method 100 then comprises a step 112 of fixing at least one cover over the padding 56. One cover can cover the whole backrest padding. Alternatively, several covers can cover separate portions of the backrest padding.

[0078] The invention is not limited solely to the examples described above. On the contrary, the invention is capable of numerous variations accessible to one skilled in the art.

[0079] Thus, in the example illustrated, the front part of the backrest trimming 18 comprised modules, especially lateral modules 40, 42. Alternatively, however, the backrest upholstery 18, in particular its front part intended to be in contact with an occupant of the vehicle seat 10, may be implemented in another form, in particular as a single unit without separate modules. Especially, the backrest trimming 18 can not comprise any lateral modules 40, 42.

[0080] Moreover, the description specifically refers to the fixation of a padding onto a backrest frame 17. However, one with ordinary skills in the art understands that the teaching of the present description applies to the fixation of a padding to a frame of any vehicle seat element, such as a seating portion, a headrest or an armrest.

Claims

Claims[Revendication 1] Vehicle seat element (13; 16; 34), especially backrest (16) of a vehicle seat (10), comprising a frame (14; 17; 35) and a trimming (15; 18; 36) directly or indirectly fixed to the frame (14; 17; 35), the trimming (15; 18; 36) comprising a padding, the padding comprising, preferably consisting in, a mat (56) of an entanglement of thermoplastic fibers forming loops welded together, the fibers being made of a material including a polymer, the mat (56) comprising at least one first portion (56a) extending on a first face (17A) of the frame (17), destined to be oriented toward an occupant of the vehicle seat (10), and a first and a second tabs (56i ; 562) extending at least partially on a second face (17B) of the frame (17), opposed to the first face (17A) of the frame (17), wherein at least one overlapping portion of the first tab (56i) overlaps at least one overlapped portion of the second tab (562) on the second face (17B) of the frame (17) and wherein the overlapping portion of the first tab (56i) and the overlapped portion of the second tab (562) are fixed together.[Revendication 2] Vehicle seat element according to claim 1 , wherein the overlapping portion of the first tab (56i) and the overlapped portion of the second tab (562) are fixed together by ultrasonic welding.[Revendication 3] Vehicle seat element according to claim 1 or 2, wherein the overlapping portion of the first tab (56i) and the overlapped portion of the second tab (562) are fixed together along a fixing portion (80), said fixing portion (80) comprising separate strips (82), preferably with enlarged extremities (84).[Revendication 4] Vehicle seat element according to one of claims 1 to 3, wherein the overlapping portion of the first tab (56i) and the overlapped portion of the second tab (562) are fixed together along a fixing portion (80), wherein the fixing portion (80) is flush with the first and second tabs (56i, 562), outside of the overlapping portion of the first tab (56i) and the overlapped portion of the second tab (562), on its face oriented opposite to the frame (17).[Revendication 5] Vehicle seat element according to any one of claims 1 to 4, wherein the trimming includes a padding support (54) fixed onto the frame (17), the mat (56) being fixed around at least one end of the padding support (54).[Revendication 6] Vehicle seat element according to claim 5, wherein the padding support (54) comprises a portion extending on the first face (17A) of the frame (17) and a portion (62) extending on the second face (17B) of the frame (17).[Revendication 7] Vehicle seat element according to claim 6, wherein the padding support (54) extends in a U-shape around an extremity (174) of the frame (17).[Revendication 8] Vehicle seat element according to any of the preceding claims, wherein the vehicle seat element is one among:- a backrest (16) of a vehicle seat (10);- a cushion (13) of a vehicle seat (10);- a headrest (34) of a vehicle seat (10);- an armrest.[Revendication 9] A method for manufacturing a vehicle seat element (13; 16; 34) according to any one of the preceding claims, comprising the steps of:- providing the frame (14; 17; 35) of the vehicle seat element (13; 16; 34) and the mat ofthe trimming (56); - folding the mat of the trimming (56) so that at least one first portion (56a) extends on a first face(17A) of the frame (17), destined to be oriented toward an occupant of the vehicle seat (10), and a first and a second tabs (56i ; 562) extend at least partially on a second face (17B) of the frame (17), opposed to the first face (17A) of the frame (17), wherein at least one overlapping portion of the first tab (56i) overlaps at least one overlapped portion of the second tab (562) on the second face (17B) of the frame (17); and- fixing together the at least one overlapping portion of the first tab (56i) with the at least one overlapped portion of the second tab (662).[Revendication 10] Method according to claim 9, wherein the overlapping portion of the first tab (56i) and the overlapped portion of the second tab (562) are fixed together by ultrasonic welding.

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