Patent Publication Number: US-2022227266-A1

Title: Vehicle seat backrest

Description:
PRIORITY CLAIM 
     This application claims priority to French Patent Application No. FR2100488, filed Jan. 19, 2021, which is expressly incorporated by reference herein. 
     BACKGROUND 
     The present disclosure relates to a vehicle seat backrest, in particular of a motor vehicle. Also described is a vehicle seat comprising such a backrest, and a method of manufacturing such a vehicle seat backrest. 
     SUMMARY 
     According to the present disclosure, a vehicle seat backrest comprises a backrest frame, at least one headrest attachment rod, and a backrest upholstery. 
     In illustrative embodiments, the backrest upholstery comprises at least one rear central shell, fixed to a rear face of the backrest frame, the rear central shell comprising at least one hole traversed by the at least one headrest attachment rod. 
     In illustrative embodiments, the hole in the rear central shell helps to guide the positioning of this rear central shell on the backrest frame. It is thus possible to obtain a very precise positioning of the rear central shell, even with the help of automated systems. 
     In illustrative embodiments, a method of assembly comprises one or more of the following features, alone or in combination: 
     the at least one hole is formed on an upper rim of the rear central shell; 
     the rear central shell comprises a hole, preferably two holes, each hole being traversed by a single respective headrest attachment rod; 
     the backrest upholstery comprises at least two rear side shells, the rear side shells preferably being fixed to the rear central shell, in particular by snap fitting (also referred to as elastic interlocking); 
     the backrest upholstery also comprises a front central upholstery module, comprising at least one backrest padding, the front central upholstery module being fixed to a front face of the backrest frame; 
     the front central upholstery module comprises at least one hole traversed by the at least one headrest attachment rod, the front central upholstery module preferably partially covering the rear central shell in the vicinity of the at least one headrest attachment rod; 
     the backrest frame comprises at least one upper crossmember, integral with the at least one headrest attachment rod, and a lower crossmember, the front central upholstery module comprising fixing means for attachment to the upper crossmember and/or to the lower crossmember, in particular snap fitting fixing means; 
     the front central padding module comprises a support for the padding, the padding being for example overmolded on the support; 
     the backrest upholstery comprises at least two front side upholstery modules, the at least two front side upholstery modules each comprising a support fixed to the backrest frame and a padding fixed to the respective support, the rear central shell preferably being fixed to the supports of the front side upholstery modules, in particular by snap fitting; and 
     the rear side shells are further fixed to the supports of the front side upholstery modules, in particular by snap fitting. 
     In illustrative embodiments, also described is a vehicle seat backrest assembly comprising a backrest as described above, in all its combinations, and a headrest, the headrest comprising a headrest frame and a headrest upholstery, the headrest frame being fixed to the at least one headrest attachment rod. 
     In illustrative embodiments, a motor vehicle seat is also described comprising a seating portion with a seating portion frame and a backrest as described above, in all its combinations, in particular in a seat backrest assembly as described above, in all its combinations, the backrest frame being fixed to the seating portion frame, preferably so as to be able to pivot about a transverse axis. 
     In illustrative embodiments, a method of manufacturing a seat backrest as described above in all its combinations is also described, comprising the steps of: 
     i) providing a backrest frame to which is fixed at least one headrest attachment rod; 
     ii) providing a rear central shell comprising at least one hole suitable for receiving the at least one headrest attachment rod; 
     iii) positioning the rear central shell on the backrest frame so that the at least one headrest attachment rod is received in the at least one hole; and 
     iv) fixing the rear central shell, in particular by snap fitting. 
     In illustrative embodiments, the method of manufacturing a seat backrest may further comprise a step 
     a) of providing two side upholstery modules and fixing the side upholstery modules on the backrest frame, step a) preferably being before step iii), the rear central shell more preferably being fixed to the side upholstery modules. 
     Additionally or alternatively, the method of manufacturing a seat backrest may comprise a step b) of providing two rear side shells and fixing the rear side shells, step b) preferably being subsequent to step iv) and to step a) where appropriate, the rear side shells preferably further being fixed to the side upholstery modules, where appropriate. 
     Additionally or alternatively, the method of manufacturing a vehicle seat backrest may comprise a step c) of providing a front central upholstery module and fixing the front central upholstery module on the backrest frame, preferably by snap fitting, step c) more preferably being subsequent to steps iv), a) and/or b), where appropriate. 
     Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of illustrative embodiments exemplifying the best mode of carrying out the disclosure as presently perceived. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       The detailed description particularly refers to the accompanying figures in which: 
         FIG. 1  schematically shows an example of a vehicle seat in a section view; 
         FIG. 2  is a flowchart of an exemplary method of manufacturing the vehicle seat backrest of  FIG. 1 ; 
         FIG. 3 a    schematically illustrates a first step of the method of  FIG. 2 ; 
         FIG. 3 b    schematically illustrates a detail of  FIG. 3   a;    
         FIG. 4  schematically shows a perspective view of the front face of the seat backrest blank at the end of the step of  FIG. 3   a;    
         FIG. 5  schematically illustrates a second step of the method of  FIG. 2 ; 
         FIG. 6  schematically illustrates a third step of the method of  FIG. 2 ; 
         FIG. 7  schematically illustrates a fourth step of the method of  FIG. 2 ; 
         FIG. 8  shows a perspective view of a front face of the seat backrest obtained at the end of the step illustrated in  FIG. 7 ; and 
         FIG. 9  shows a perspective view of a rear face of the seat backrest obtained at the end of the step illustrated in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     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. 
     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. 
       FIG. 1  schematically shows a motor vehicle seat  10  mounted on a slide mechanism  12 . 
     The seat  10  includes a seating portion  13 , with a seating portion frame  14  and seating portion upholstery  15 , on which is mounted a backrest  16 , with a backrest frame  17  and backrest upholstery  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. 
     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. 
     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. 
     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 . 
     The seat  10  further comprises a headrest  34 . The headrest  34  comprises a headrest frame  35  and a headrest upholstery  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 . 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)  35  to allow this adjusting of the positional height of the headrest  34 . The headrest upholstery  36  and/or the backrest upholstery  18  may cover all or part of the headrest attachment rod(s)  38 , for example to improve the aesthetics of the vehicle seat  10 . 
     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. 
     As illustrated in  FIG. 2 , the method  100  comprises a first step  102  of providing a backrest frame  17 . As illustrated in  FIG. 3 a   , the backrest frame  17  comprises a first upright  17   1 , a second upright  17   2 , a first crossmember  17   3 , hereinafter called “lower crossmember  17   3 ”, and a second crossmember  17   4 , hereinafter called “upper cross member  17   4 ”. The uprights  17   1 ,  17   2  and the crossmembers  17   3 ,  17   4  form a backrest frame  17  in the form of a framework. To achieve this, the uprights  17   1 ,  17   2 , and the crossmembers  17   3 ,  17   4  can be fixed together, in particular welded together. Alternatively, the backrest frame  17  is one piece, being for example molded. 
     Here, the headrest attachment rods  38  are already fixed on the upper crossmember  17   4  of the backrest frame  17  at this first step  102 . Alternatively, however, these headrest attachment rods  38  may be attached to the upper crossmember  17   4  of the backrest frame  17  in a later step. 
     During a second step  104  of the manufacturing method  100 , a first side upholstery module  40  and a second side module upholstery  42  are fixed to the front face  17 A of the backrest frame  17 , visible in  FIG. 3 a   , on a respective upright  17   1 ,  17   2  of the backrest frame  17 . Thus, a side upholstery module  40 ,  42  is arranged on each side of the backrest frame  17 . The front face  17 A 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  17 B of the backrest frame  17  is the face opposite to the front face  17 A. 
     Each side upholstery module  40 ,  42  here comprises padding in the form of a foam block  44 ,  46 , each foam block  44 ,  46  being fixed on a respective support  48 ,  50 . For example, each foam block  44 ,  46  is overmolded on the respective support  48 ,  50 . Each support  48 ,  50  may be fixed to the respective upright  17   1 ,  17   2  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  comprises a respective upright  51 ,  53  with snap fitting reliefs  52  making it possible to fix on the upright  51 ,  53 , here by snap fitting, an airbag support  54  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  54 . Other shapes of the snap fitting reliefs  52  are accessible to those skilled in the art. 
     The first side upholstery module  40  intended to be positioned centermost in the motor vehicle equipped with the seat  10 , here further comprises a side airbag safety device  56 . Such an airbag device  56  aims to avoid direct head-to-head impacts between the occupants of two seats arranged transversely, one next to the other. The airbag system  56  is at least partially covered by the foam block  44  of the first side upholstery module  40 . 
     The method of manufacturing  100  then continues with a step  106  of fixing a rear central shell  58  on the backrest frame  17 . The rear central shell  58  makes it possible to obtain a very aesthetic backrest of the seat  10 . The rear central shell can be without foam, since it is not intended to provide support for an occupant of the vehicle seat  10 . 
     Here, it is noteworthy that an upper rim  58   1  of the rear central shell  58  has two holes  60  each suitable for receiving one of the respective headrest attachment rods  38 . It is thus possible to install the rear central shell  58  on the backrest frame  17 , guiding this installation by the receiving of the headrest attachment rods  38  in the openings  60 . The installation of the rear central shell  58  is greatly facilitated. Such an implementation can thus be carried out in an efficient manner by means of an automated system. The fixing of the rear central shell  58  is then carried out, in the example illustrated, by snap fitting of second snap fitting reliefs  62  of the supports  48 ,  50  of the side upholstery modules  40 ,  42 , with additional reliefs  64  of the rear central shell  58 . Here, the second snap fitting reliefs  62  take the form of deformable studs having a bead at the end, each received in a respective opening  64  in the rear central shell  58 , of smaller diameter than the diameter of the bead of the studs. Here again, this fixing, achieved by moving the rear central shell  58  relative to the backrest frame  17 , can be achieved by means of one or more automated systems. 
     The fixing of the rear central shell  58  may however be carried out in an alternative or complementary manner, using any fixing means accessible to those skilled in the art, in particular by screwing, welding, riveting, or forcibly inserting a fixing relief in a complementary relief. Such fixing means may also be implemented by means of one or more automated systems. 
     Also, in the example described, the rear central shell  58  is fixed to the side upholstery modules  40 ,  42 . Additionally or alternatively, the rear central shell  58  is fixed directly to the backrest frame  17 , in particular to the uprights  17   1 ,  17   2  and/or to the lower crossmember  17   3 . 
     It can be noted here that the rear central shell  58  has openings  66 , distinct from the holes  60 , allowing free access to third snap fitting reliefs  68  of the side upholstery modules  40 ,  42 , in particular the supports  48 ,  50  of the side upholstery modules  40 ,  42 . 
     The method of manufacturing  100  then continues with a step  108  of fixing the rear side shells  70 ,  72 , here so as to cover at least part of the lateral ends of the rear central shell  58 . To do this, each rear side shell  70 ,  72  comprises fixing means  74 , here in the form of snap fitting reliefs complementary to the third snap fitting reliefs  68  of the supports  48 ,  50  of the side upholstery modules  40 ,  42 . In addition, each rear side shell  70 ,  74  may include a relief  76  intended to be received in a complementary housing  78  of the corresponding side upholstery module  40 ,  42 , to facilitate the placement and fixing of the rear side shells  70 ,  72 . 
     Here again, the rear side shells  70 ,  72  serve an aesthetic function, particularly in that they conceal the fixing means for the rear central shell  58 . As these rear side shells  70 ,  72  are not intended to serve as a support for an occupant of the vehicle seat, they may also be without padding, in particular foam. 
     The method of manufacturing  100  then continues with a final step  110  of fixing a front central upholstery module  80 . 
     As illustrated in  FIG. 7 , the front central upholstery module  80  comprises a support  82  and padding, here in the form of a foam block  84 , fixed on the support  82 . The foam block  84  may in particular be overmolded on the support  82 . 
     The support  82  of the front central upholstery module  80  may comprise at least three parts assembled together to form an upper part  82   1 , a middle part  82   2 , and a lower part  82   3  of the support  82 . 
     The upper part  82   1  may be shaped to facilitate the installation of the central upholstery module  80  on the backrest frame  17 . To do so, the upper part  82   1  and the foam block  84  may have openings (not visible in the figures) suitable for receiving the headrest attachment rod(s)  38 . Thus, this upper part  82   1  is placed above the rear central shell  58 , in the vicinity of the headrest attachment rods  38 . The central upholstery module  80  thus at least partially covers, preferably completely covers, the rim  58   1  of the rear central shell  58 . To achieve this, the upper end of the front central upholstery module  80  may be curved. 
     The middle part  82   2  has the function of supporting the foam block  84 , where the occupant of the vehicle seat  10  primarily bears against the seat backrest  16 . The middle part  82   2  thus advantageously provides sufficient mechanical resistance so that the foam block  84  does not sink in completely when an occupant of the vehicle seat  10  leans on the seat backrest  16 . However, the middle part  82   2  is advantageously still relatively flexible in order to ensure the comfort of the occupant of the vehicle seat  10 . 
     In addition, the middle part  82   2  can support one or more members making it possible to fulfill one or more comfort and/or safety functions for the occupant of the seat  10 . For example, a fan may be attached to this central part, suitable for blowing air towards the occupant of the seat, through openings  86  in the central upholstery module  80 . 
     The middle part  82   2  can have different forms. Here, the middle part  82   2  is in the form of a flexible plate, in particular more flexible than the upper part  82   1  and/or the lower part  82   3 . Alternatively, the middle part  82   2  is composed of spring wires extending between the upper part  82   1  and the lower part  82   3 , to ensure that the foam block  84  is held in position, with elastic support for this foam block  84 . 
     Finally, the lower part  82   3  is shaped here to ensure the attachment of the central front upholstery module  80 , in this case on the backrest frame  17 . Here, this lower part  82   3  is curved at its lower end and has snap fitting reliefs (not shown in the figures) suitable for engaging with complementary reliefs on the lower crossmember  17   3  of the backrest frame  17 . As can be seen in particular in  FIG. 9 , once the central front upholstery module  80  is attached to the backrest frame  17 , the foam block  84  extends locally under the rear central shell  58 . In other words, part of the foam block  84  of the central upholstery module  80  extends between the backrest frame  17 , in particular the lower crossmember  17   3 , and the rear central shell  58 . A very aesthetic finish is thus obtained for the backrest upholstery  18 . In particular, the fixing means for all of the elements forming the backrest upholstery  18  are concealed. 
     However, other fixing means for attaching the central upholstery module  80  on the backrest frame  17  are conceivable, in particular such as screwing, welding, riveting, or forcibly inserting a fixing relief into a complementary relief. Additionally or alternatively, the central upholstery module  80  may be fixed to the rear central shell  58  and/or to the side upholstery modules  40 ,  42  or even to the rear side shells  70 ,  72 . 
     It should be noted that the elements forming the backrest upholstery  18  may be fixed successively, in particular by means of automated systems. As such, production of the upholstery solely by means of upholstery modules and shell modules allows easy manipulation, in particular by automated systems. 
     A headrest  34  may lastly be fixed on the headrest attachment rods  38 . Advantageously, the headrest upholstery  36  covers the headrest attachment rod(s)  38 , such that the backrest  18  and the headrest  34  assembly thus obtained is particularly aesthetic. 
     The present disclosure is not limited solely to the examples described above. On the contrary, the present disclosure is capable of numerous variations accessible to those skilled in the art. 
     Thus, in the example illustrated, the front part of the backrest upholstery  18  is produced by means of modules  40 ,  42 ,  80 . As indicated above, such production by means of modules  40 ,  42 ,  80  makes it possible to automate easily the manufacture of the backrest  16  while obtaining a highly aesthetic appearance of the backrest  16 . 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. 
     Also, each upholstery module  40 ,  42 ,  80  may comprise a cover covering all or part of the respective foam block  44 ,  46 ,  84 . The cover may in particular be placed in the mold used for overmolding the foam block  44 ,  46 ,  84  on the respective support  48 ,  50 ,  82 . The cover then adheres to the foam block  44 ,  46 ,  84 . Alternatively, the cover may be fixed to the foam block  44 ,  46 ,  84  and/or to the support  48 ,  50 ,  82  after the foam block  44 ,  46 ,  84  has been formed. In other words, the cover may be attached onto the foam block  44 ,  46 ,  84  and/or onto the support  48 ,  50 ,  82 . The cover is then fixed by any means accessible to those skilled in the art. 
     According to yet another variant, a single cover is used to cover the three foam blocks  44 ,  46 ,  84  of the upholstery modules  40 ,  42 ,  80 . Here again, in this case, the cover is advantageously attached onto the foam blocks  44 ,  46 ,  84  and/or onto the respective supports  48 ,  50 ,  82  of the upholstery modules  40 ,  42 ,  80 , or even onto the backrest frame  17  and/or the rear central shell  58 . Here again, the cover is fixed by any means accessible to those skilled in the art. 
     Advantageously, the upholstery of each upholstery module  40 ,  42 ,  80  is independent of the other two, as described above. Alternatively, however, it is conceivable that a foam block, for example, is common to several upholstery modules, in particular to all of the upholstery modules  40 ,  42 ,  80 . 
     It can be noted that here the side upholstery modules  40 ,  42  pre-exist their attachment to the backrest frame  17 . Thus, these side upholstery modules  40 ,  42  are not produced by overmolding the backrest frame  17  and/or structural elements already integral with the backrest frame  17 . This does not prevent the foam blocks  44 ,  46 ,  84  of the various upholstery modules  40 ,  42 ,  80  from being produced by overmolding a possible support of the respective upholstery module  48 ,  50 ,  82 . However, such overmolding is carried out prior to fixing the support in question to the backrest frame  17 . 
     A backrest ( 16 ) of a vehicle seat ( 10 ) comprises a backrest frame ( 17 ), at least one headrest attachment rod ( 38 ), and a backrest upholstery ( 18 ). The backrest upholstery ( 18 ) comprises at least one rear central shell ( 58 ), fixed to a rear face ( 17 B) of the backrest frame ( 17 ). The rear central shell ( 58 ) comprises at least one hole ( 60 ) traversed by the at least one headrest attachment rod ( 38 ). 
     A comparative vehicle seat backrest may be produced fixing upholstery on a backrest frame. The backrest frame provides for a rigid backrest, while the upholstery provides for comfort and aesthetics of the backrest. 
     The comparative upholstery comprises a padding covered with one or more covers to protect the padding and/or to hold it in position on the backrest of the seat. 
     However, such a comparative backrest is difficult to produce using automated systems. In particular, the precise placement of the padding can be difficult. 
     It has been proposed to implement the rear part of the upholstery by means of a shell without padding. Indeed, padding on the rear part of the backrest appears unnecessary since this rear part does not serve as a support for a seat occupant. 
     However, such a shell is also difficult to manipulate, position precisely, and fix on the backrest frame, by means of automated systems. 
     This disclosure aims to improve the situation. 
     To this end, a vehicle seat backrest is described comprising a backrest frame, at least one headrest attachment rod, and a backrest upholstery, the backrest upholstery comprising at least one rear central shell, fixed to a rear face of the backrest frame, the rear central shell comprising at least one hole traversed by the at least one headrest attachment rod. 
     Thus, advantageously, the hole in the rear central shell helps to guide the positioning of this rear central shell on the backrest frame. It is thus possible to obtain a very precise positioning of the rear central shell, even with the help of automated systems. 
     According to preferred embodiments, the method of assembly comprises one or more of the following features, alone or in combination: 
     the at least one hole is formed on an upper rim of the rear central shell; 
     the rear central shell comprises a hole, preferably two holes, each hole being traversed by a single respective headrest attachment rod; 
     the backrest upholstery comprises at least two rear side shells, the rear side shells preferably being fixed to the rear central shell, in particular by snap fitting (also referred to as elastic interlocking); 
     the backrest upholstery also comprises a front central upholstery module, comprising at least one backrest padding, the front central upholstery module being fixed to a front face of the backrest frame; 
     the front central upholstery module comprises at least one hole traversed by the at least one headrest attachment rod, the front central upholstery module preferably partially covering the rear central shell in the vicinity of the at least one headrest attachment rod; 
     the backrest frame comprises at least one upper crossmember, integral with the at least one headrest attachment rod, and a lower crossmember, the front central upholstery module comprising fixing means for attachment to the upper crossmember and/or to the lower crossmember, in particular snap fitting fixing means; 
     the front central padding module comprises a support for the padding, the padding being for example overmolded on the support; 
     the backrest upholstery comprises at least two front side upholstery modules, the at least two front side upholstery modules each comprising a support fixed to the backrest frame and a padding fixed to the respective support, the rear central shell preferably being fixed to the supports of the front side upholstery modules, in particular by snap fitting; and 
     the rear side shells are further fixed to the supports of the front side upholstery modules, in particular by snap fitting. 
     According to another aspect, also described is a vehicle seat backrest assembly comprising a backrest as described above, in all its combinations, and a headrest, the headrest comprising a headrest frame and a headrest upholstery, the headrest frame being fixed to the at least one headrest attachment rod. 
     A motor vehicle seat is also described comprising a seating portion with a seating portion frame and a backrest as described above, in all its combinations, in particular in a seat backrest assembly as described above, in all its combinations, the backrest frame being fixed to the seating portion frame, preferably so as to be able to pivot about a transverse axis. 
     A method of manufacturing a seat backrest as described above in all its combinations is also described, comprising the steps of: 
     i) providing a backrest frame to which is fixed at least one headrest attachment rod; 
     ii) providing a rear central shell comprising at least one hole suitable for receiving the at least one headrest attachment rod; 
     iii) positioning the rear central shell on the backrest frame so that the at least one headrest attachment rod is received in the at least one hole; and 
     iv) fixing the rear central shell, in particular by snap fitting. 
     The method of manufacturing a seat backrest may further comprise a step a) of providing two side upholstery modules and fixing the side upholstery modules on the backrest frame, step a) preferably being before step iii), the rear central shell more preferably being fixed to the side upholstery modules. 
     Additionally or alternatively, the method of manufacturing a seat backrest may comprise a step b) of providing two rear side shells and fixing the rear side shells, step b) preferably being subsequent to step iv) and to step a) where appropriate, the rear side shells preferably further being fixed to the side upholstery modules, where appropriate. 
     Additionally or alternatively, the method of manufacturing a vehicle seat backrest may comprise a step c) of providing a front central upholstery module and fixing the front central upholstery module on the backrest frame, preferably by snap fitting, step c) more preferably being subsequent to steps iv), a) and/or b), where appropriate.