FR3125486A1 - Seat back frame including bottom cross member - Google Patents

Abstract

Seat back frame comprising a lower crossbar The seat back frame (1) comprising at least two lateral uprights (2) each extending between a lower edge (14) and an upper edge (16) in a direction of elevation, at least one lower crosspiece (4) extending in a transverse direction substantially perpendicular to the direction of elevation, said lower crosspiece (4) joining the two side uprights (2) in the vicinity of the lower edges (14) of said side uprights (2), and at least one upper crosspiece (6) extending in the transverse direction and joining the two side uprights (2) in the vicinity of the upper edges (16) of said side uprights (2). The bottom rail (4) comprises at least one transverse rib (27) extending without interruption from one transverse end of the bottom rail (4) to the other transverse end. Figure for abstract:1

Description

Seat back frame including bottom cross member

The present invention relates to a seat back frame, of the type comprising at least two side uprights each extending between a lower edge and an upper edge in a direction of elevation, at least one lower cross member extending in a transverse direction substantially perpendicular to the direction of elevation, said lower crosspiece joining the two side uprights in the vicinity of the lower edges of the said side uprights, and at least one upper crosspiece extending in the transverse direction and joining the two side uprights in the vicinity of the upper edges of said side uprights.

The invention also relates to a vehicle seat, the back of which comprises such a frame.

The invention applies for example to a motor vehicle seat. The back of such a seat generally comprises a frame, a body, for example made of foam, mounted on the frame and a headrest also mounted on the frame.

The reinforcement is for example formed of metal sections assembled together by welding. More particularly, the frame comprises two side uprights connected to each other by means of a lower crosspiece and an upper crosspiece.

The crosspieces are welded to the side uprights when assembling the frame. More particularly, the ends of the crosspieces are for example welded by a weld line on the side uprights.

However, in the event of an impact on the seat, in particular following a frontal or side impact on the vehicle, the welds between the lower cross member and the side uprights may not be strong enough to prevent excessive deformation of the frame, or even a break in the connection between the crosspieces and one or more uprights, which may endanger the occupant of the seat. More specifically, a frontal impact may cause the head restraint to move too far in the front-rear direction following twisting of the backrest frame. A test called "whiplash" in the Euro NCAP standard makes it possible to determine whether the frame exhibits satisfactory behavior by limiting the movement of the head restraint in the event of a frontal impact. During a side impact, the deployment of a safety bag between the seats tends to cause undesirable deformation of the frame. A test called "far side" (remote side) in the Euro NCAP standard makes it possible to determine whether the frame exhibits satisfactory behavior by limiting the deformation of the backrest following the deployment of a safety cushion between the seats in the event of a side impact. .

One of the aims of the invention is to provide a more robust seat back frame while remaining light and making it possible to limit the deformations of the frame in the event of a frontal or lateral impact on the seat. In particular, the reinforcement must respond satisfactorily to the whiplash and far side tests of the Euro NCAP standard.

To this end, the invention relates to a seat back frame of the aforementioned type, in which the lower cross member comprises at least one transverse rib extending without interruption from one transverse end of the lower cross member to the other transverse end.

By providing a rib extending without interruption on the lower crosspiece from one side upright to the other of the frame, this frame is made more robust and capable in particular of responding satisfactorily to the regulatory standards relating to the behavior of a vehicle seat in the event of an impact.

According to other optional characteristics of the seat back frame according to the invention, taken in isolation or according to any technically possible combination:

- at least the lower crosspiece comprises at least two projecting zones extending respectively opposite each side upright, each projecting zone of the lower crosspiece being welded to the side upright extending opposite said projecting zone;

- each side upright comprises at least one first upper projection extending in the transverse direction in the vicinity of the upper edge and opposite the upper crosspiece, the upper crosspiece being welded at least to the first upper projections of the two side uprights;

- each side upright comprises at least one main wall extending in the direction of elevation and in a longitudinal direction substantially perpendicular to the direction of elevation and to the transverse direction, a first transverse flank and a second transverse flank, the first transverse flank and the second transverse flank extending on either side of the main wall in the direction of elevation and in the transverse direction, the lower crosspiece being fixed to the first lateral flank and the first upper projection extending to from the second lateral flank;

- the side uprights each further comprise a second upper projection extending in the transverse direction from the first side flank of each side upright in the vicinity of the upper edge and facing the upper crosspiece, said upper crosspiece being further welded to the second upper protrusions;

- the two projecting zones of the lower crosspiece each extend at a transverse end of the lower crosspiece, each projecting zone extending in the direction of elevation above said transverse end, each transverse end and each zone projecting being welded to a side upright;

- the upper crosspiece comprises a profile comprising a main wall extending in the direction of elevation and the transverse direction, an upper side and a lower side extending on either side of the main wall in substantially perpendicular planes to the main wall, the upper side extending above the lower side in the direction of elevation;

- The main wall is welded to the first upper projections of the two side uprights;

- the upper flank and the lower flank each comprise at least one through hole for passage of a headrest rod, the through hole of the upper side extending opposite the through hole of the lower side in the direction d 'elevation ;

- the upper crosspiece comprises at least one upper wall extending in the elevation direction and the transverse direction from and above the upper sidewall in the elevation direction, the main wall and upper wall extending on either side and on the other side of the upper side in a longitudinal direction substantially perpendicular to the direction of elevation and to the transverse direction;

- the upper wall comprises a transverse fold extending without rupture from one transverse end of the upper wall to the other;

- the upper crosspiece comprises at least one lower wall extending in the elevation direction and the transverse direction from and below the lower flank in the elevation direction, the main wall and lower wall extending on either side and on the other side of the lower side in a longitudinal direction substantially perpendicular to the direction of elevation and to the transverse direction;

- the transverse rib has a height, measured in the direction of elevation, of between 10 mm and 25 mm and/or a depth, measured in a longitudinal direction substantially perpendicular to the transverse direction and to the direction of elevation, greater than or equal to 3 mm.

According to another aspect, the invention also relates to a vehicle seat comprising a backrest and a seat, the backrest comprising at least one frame as described above, a body mounted on said frame and a headrest mounted on the crosspiece top of said frame.

Other aspects and advantages of the invention will appear on reading the following description, given by way of example and made with reference to the appended drawings, in which:

- there is a schematic representation in perspective of a seat back frame according to the invention, a headrest being mounted on this frame,

- there is an enlargement of an area of the at the level of the attachment between a lower crosspiece and a side upright of the frame of the ,

- there is an enlargement of an area of the at the level of the attachment between an upper crosspiece and a side upright of the frame of the ,

- there is a schematic representation in perspective of a lower cross member of the seat back frame of the , And

- there is a schematic representation in perspective of an upper cross member of the seat back frame of the .

In the description, a direction of elevation corresponding to the height of a seat back is defined. The direction of elevation corresponds for example to the height of a vehicle when the seat is mounted in this vehicle and the backrest is in the upright position. A transverse direction is also defined extending substantially perpendicular to the direction of elevation and corresponding to the width of the seat back. When the seat is mounted in a vehicle and faces the windshield of the vehicle, the transverse direction corresponds for example to the width of the vehicle. A longitudinal direction substantially perpendicular to the direction of elevation and to the transverse direction is also defined. When the seat is mounted in a vehicle and faces the windshield of the vehicle, the longitudinal direction corresponds for example to the front-rear direction of the vehicle. The term "significantly" is used to indicate that an element may deviate slightly from the direction in which it extends. Thus, the elements do not necessarily extend straight along the direction in which it extends but may have variations with respect to this direction, as shown in the figures. Thus, by substantially, we indicate that an element is likely to undergo a variation of up to 10° with respect to the direction in which this element extends.

With reference to the , there is described a seat back frame 1 comprising at least two side uprights 2, a lower cross member 4 and an upper cross member 6.

Each side upright 2 is for example formed by a metal profile. The profile comprises a main wall 8 extending substantially in the direction of elevation and in the longitudinal direction. The main wall 8 extends mainly in the direction of elevation, ie its dimension in this direction is greater than its dimension in the longitudinal direction. The profile further comprises a first lateral flank 10 and a second lateral flank 12 each extending substantially in the direction of elevation and in the transverse direction from the main wall 8. Each lateral flank extends mainly in the direction elevation, that is to say that its dimension in this direction is greater than its dimension in the transverse direction. The first lateral flank 10 and the second lateral flank 12 extend on either side of the main wall 8 so that the section has a substantially U-shaped section in a plane substantially perpendicular to the direction of elevation. When the frame 1 is mounted, the cavities formed between the side flanks and the side wall of the two uprights 2 face each other. In other words, the first lateral flank 10 and the second lateral flank 12 of an upright 2 extend towards the other upright 2 of the frame 1. Each upright 2 extends between a lower edge 14 and a upper edge 16 in the elevation direction. In order to improve the behavior of the uprights in the event of an impact, at least one of the side flanks of each upright comprises, for example, an elevation rib 17 extending in the direction of elevation of the lower edge 14 up to the vicinity of the upper edge 16, as seen in the . Such a rib forms a projecting zone in the longitudinal direction in the lateral flank 12 extending towards the other lateral flank 10 and makes it possible to improve the inertia of the upright 2 in order to limit the deformation, and in particular a torsion, of the amount 2 in the event of an impact.

When the backrest is mounted on a seat, the backrest is connected to the seat cushion at the level of the lower edge 14 of the uprights 2, the backrest receives for example a headrest 18 at the level of the upper edge 16 of the uprights 2, as represented on the .

According to an embodiment shown in Figs. 1 and 3, each side upright 2 further comprises at least one first upper projection 22 extending in the transverse direction in the vicinity of the lower edge 14. By the vicinity, it is meant that the first upper projection 22 is closer to the upper edge 16 than the lower edge 14, more particularly that it is closer to the upper edge 16 than to the center of the upright 2. According to one embodiment, the first upper projection 22 extends at a distance less than 80 mm from the upper edge 16. The upper projection 22 projects in the transverse direction of the upright 2, that is to say it extends beyond the first and second side flanks 10, 12 in the transverse direction. In other words, the first upper projection 22 locally increases the dimension of the upright 2 in the transverse direction in the vicinity of the upper edge 16. According to the embodiment shown in the and 3, the first upper projection 22 extends projecting from the second lateral flank 12 in the transverse direction in the vicinity of the upper edge 16 and is integral with this second lateral flank 12. The first upper projection 22 has for example a shape substantially frustoconical, the dimension of the first upper projection 22 in the transverse direction being substantially between 0 mm and 65 mm, preferably between 20 mm and 60 mm.

According to a particular embodiment, also shown in Figs. 1 and 3, each side upright 2 further comprises a second upper projection 24 extending in the transverse direction in the vicinity of the upper edge 14. According to the embodiment shown in Figs. 1 and 3, the second upper projection extends in the vicinity of the upper edge 16 but is however farther from it than the first upper projection 22, that is to say that the second upper projection 24 extends at a lower height to that of the first upper projection 22 in the direction of elevation, while remaining close to the upper edge 16. Thus, according to one embodiment, the second upper wall 24 extends to a distance greater than 80 mm and less than 200 mm from the upper edge 16. According to the embodiment shown in the and 3, the second upper projection 24 extends projecting from the first lateral flank 10 in the transverse direction in the vicinity of the upper edge 16 and is integral with this first lateral flank 10. The second upper projection 22 has for example a shape substantially triangular, the height of the triangle extending in the transverse direction and having a dimension between 20 mm and 50 mm. In other words, the first and second upper projections 22, 24 extend over two different side flanks of the uprights 2.

The lower crosspiece 4 extends in the transverse direction between the two side uprights 2 in the vicinity of the lower edges 14 thereof. More particularly, the lower crosspiece 4 joins the two side uprights to each other in the vicinity of the lower edges 14.

The lower crosspiece 4 is for example formed by a metal profile comprising a fixing wall 26 and a bottom wall 28.

The fixing wall 26 extends mainly in the transverse direction and, to a lesser extent, in the direction of elevation, that is to say that the dimension of the fixing wall in the transverse direction is greater than its dimension according to the direction of elevation. The fixing wall 26 comprises a transverse rib 27 extending in the transverse direction from one transverse end of the fixing wall 26 to the other without interruption, as more particularly visible on the . The transverse rib 27 extends for example hollow towards the rear in the fixing wall 26 so as to form a groove in this fixing wall 26. In other words, the rib 27 is entirely convex on the rear side of the seat. Such a rib 27 makes it possible to ensure good transmission of the forces from one upright 2 to the other, in particular in the event of a lateral impact on one of the uprights so as to transmit the energy due to the impact of this upright to the other and thus limit the deformation of the reinforcement.

According to the embodiment shown in Figs. 1 and 5, the rib 27 does not extend along a rectilinear path from one side upright 2 to the other and comprises a substantially V-shaped central zone whose bottom extends at a height lower than the height of the rest of the rib 27. It is understood, however, that the rib 27 could be straight from one side upright 2 to the other. The lower crosspiece 4 is for example made of folded sheet metal or by stamped sheet metal to form the rib 27.

The rib 27 extends under an upper flank 31 forming the upper edge of the lower crosspiece. This flank extends forward from the attachment wall 26 in the longitudinal direction and is substantially perpendicular thereto. The width of the upper flank 31, measured in the longitudinal direction, is for example greater than 15 mm, for example substantially between 15 mm and 50 mm. It is understood that the width of the upper side 31 is not necessarily constant from one side upright 2 to another.

The height h of the rib 27, represented on the , and measured in the direction of elevation between a lower edge of the groove and an upper edge of the groove, formed by the upper flank 31, is for example substantially between 10 mm and 25 mm. The height h is for example measured halfway along the transverse direction from the center of the lower crosspiece 4 and from the main wall 8 of one of the side uprights 2. It is understood that the height h of the rib is not not necessarily constant from one side upright 2 to another.

The rib 27 has a depth p, represented on the and measured between the first side blank 10 of a side upright 2 and the bottom of the rib 27 towards the rear of the seat, greater than or equal to 3 mm, preferably substantially between 4 mm and 9 mm. The depth of the rib 27 can also be measured between the fixing wall 26 and the bottom of the rib 27 towards the rear of the seat. It should be noted that the depth of the rib includes the thickness of the sheet forming the lower crosspiece 4, which is less than 1 mm, for example substantially equal to 0.8 mm. It is understood that the depth p of the rib is not necessarily constant from one side upright 2 to another.

The lower crosspiece 4 further comprises at least one projecting zone 29 at each transverse end of the fixing wall 26. Each projecting zone 29 projects in the direction of elevation of the fixing wall 26 at one end transverse of the lower crosspiece 4, as more particularly visible on the . More particularly, each projecting zone 29 extends above the attachment wall 26 and extends facing the first lateral flank 10 of an upright 2 when the frame is mounted, as shown in Figs. 1 and 2. Thus, when the frame is mounted, each transverse end of the fixing wall 26 and each protruding zone 29, which locally increases the height of the transverse end of the fixing wall 26, extend in next to the first lateral flank 10 of an upright 2 and are fixed to this first lateral flank 10 by welding. In other words, each projection zone 29 increases the recess height of the lower crosspiece on a side upright 2 and offers a larger fixing surface between the lower crosspiece 4 and the side upright. In fact, weld beads extending in the direction of elevation can then extend between the transverse ends, the projecting zones 29 and the first flank 10 of the side uprights so as to fix the lower crosspiece 4 on the uprights side over a significant height, for example substantially between 10 mm and 70 mm. Such an extended attachment ensures the robustness of the attachment between the lower crosspiece 4 and the side uprights and makes it possible to limit the torsion of the frame in the event of a frontal impact on the seat, so as to respond satisfactorily to the far side test of the Euro NCAP standard, without increasing the size or unduly weighing down the seat frame. The weld between the lower crosspiece 4 and a side upright 2 is for example a spot weld or other weld suitable for ensuring a robust connection between an upright and the lower crosspiece.

The bottom wall 28 extends mainly in the transverse direction and, to a lesser extent in the longitudinal direction, that is to say that the dimension of the bottom wall 28 in the transverse direction is greater than its dimension in the longitudinal direction. The bottom wall 28 extends from a lower edge of the fixing wall 26, of the first lateral flank 10 of the side uprights, on which the fixing wall 26 is fixed, to the second lateral flank 12 under the lower edges 14 of the side uprights 2. Thus, the bottom wall 28 closes the U-shaped section of the side uprights 2 at the lower edges 14, as shown in Figs. 1 and 2. When the seat is mounted in a vehicle and facing the windshield, the bottom wall 28 extends for example towards the front of the vehicle from the fixing wall 26.

It is understood that the lower crosspiece 4 can be fixed, for example by welding, to the side uprights 2 in places other than at the transverse ends and in the projecting zones 29 of the lower crosspiece.

The upper crosspiece 6 extends in the transverse direction between the two side uprights 2 in the vicinity of the upper edges 14 thereof. More particularly, the upper crosspiece 6 joins the two side uprights to each other in the vicinity of the upper edges 16 and can be fixed in a conventional manner thereto, for example by welding the transverse ends of the upper crosspiece 6 to the uprights. side 2.

However, according to the advantageous embodiment in which the side uprights 2 each comprise a first upper projection 22, the first upper projections 22 extend opposite the upper crosspiece 6 and are fixed thereto by welding, which allows to have an extended welding zone between each side upright 2 and the upper crosspiece 6 and thus ensure a robust connection between the side uprights 2 and the upper crosspiece 6. Indeed, the first upper projections 22 make it possible to increase the lengths of embedding in the transverse direction between the upper crosspiece 6 and the side uprights 2, as more particularly visible on the . Even more advantageously and to further improve the robustness of the attachment between the upper crosspiece 6 and the side uprights 2, according to the embodiment in which the side uprights each comprise a second upper projection 24, the second upper projections 24 are also extend opposite the upper crosspiece 6 and are fixed thereto by welding, as shown in Figs. 1 and 3.

The upper crosspiece 6 is for example formed by a metal profile comprising a main wall 30, an upper side 32 and a lower side 34.

The main wall 30 of the upper crosspiece extends mainly in the transverse direction and, to a lesser extent, in the direction of elevation, that is to say that the dimension of the main wall 30 in the transverse direction is greater than its dimension in the direction of elevation. The shape of the main wall 30 can be arranged to promote good behavior of the upper crosspiece 6 in the event of impact, for example by including a ribbed zone 31, as shown in Figs. 1 and 5. The upper crosspiece 6 is welded to the first upper projections 22 of the side uprights 2 by the transverse ends of the main wall 30. As shown in the , the weld 33 between the upper crosspiece 6 and a first upper projection 22 has for example an interrupted oval shape, which makes it possible to have a significant weld length, for example between 40 mm and 90 mm, preferably between 50 mm and 60mm.

The upper flank 32 extends mainly in the transverse direction and, to a lesser extent in the longitudinal direction. The upper flank 32 extends from an upper edge of the main wall 30 of the second lateral flank 12 of the side uprights 2, on which the main wall is fixed, to the first lateral flank 10 of the side uprights. The lower side 34 extends mainly in the transverse direction and, to a lesser extent in the longitudinal direction. The lower flank 34 extends from a lower edge of the main wall 30 of the second lateral flank 12 of the side uprights 2, on which the main wall is fixed, to the first lateral flank 10 of the side uprights. In other words, the upper and lower sides 32, 34 extend on either side of the main wall 30, the upper side 32 extending above the lower side 34 in the direction of elevation. Thus, the main wall 30, the upper flank 32 and the lower flank 34 form a U-shaped section in a plane substantially perpendicular to the transverse direction, the cavity of the U being turned towards the first flanks 10 of the side uprights 2.

According to the embodiment shown in Figs. 1 and 3, the upper 32 and lower 34 sides each comprise at least one through hole 35 for the passage of a headrest rod, the through hole of the upper side 32 extending opposite the through hole of the side lower 34 in the elevation direction. According to the embodiment shown in the figures, the upper 32 and lower 34 sides each comprise two orifices 35 extending opposite each other for the passage of two headrest rods.

According to an embodiment shown in Figs. 1 and 3, the profile forming the upper crosspiece further comprises an upper wall 36 and a lower wall 38 substantially parallel to the main wall 30 and extending respectively above the upper side 32 and below the lower side 34. More particularly, the upper wall 36 extends mainly in the transverse direction and, to a lesser extent, in the direction of elevation from the free edge of the upper flank 32. Thus, the main wall 30 and the upper wall 36 s extend on either side of the upper flank 32 in the longitudinal direction, the upper wall 36 extending above the upper flank 32 in the direction of elevation. The lower wall 38 extends mainly in the transverse direction and, to a lesser extent, in the direction of elevation from the free edge of the lower sidewall 34. Thus, the main wall 30 and the lower wall 38 extend from either side of the lower flank 34 in the longitudinal direction, the lower wall 38 extending below the lower flank 34 in the direction of elevation. According to the embodiment in which the side uprights 2 comprise second upper projections 24, these extend facing the lower wall 38 of the upper crosspiece 6 and are welded to this lower wall 38, which improves the robustness fixing the upper crosspiece 6 on the side uprights 2, as described above. As shown on the , the weld 39 between the lower wall 38 and a second upper projection has for example the shape of an interrupted oval ring having a length substantially between 40 mm and 130 mm, preferably between 50 mm and 100 mm. Note that, as also shown in the , the upper wall 36 can also be welded to the side uprights 2 by such welds 39.

According to one embodiment, the upper wall 36 further comprises a transverse fold 42 extending without rupture from one transverse end to the other of the upper wall 36 along the upper edge of the upper wall 36, at the opposite of the upper flank 34. Such a fold allows transmission of forces without breaking inertia from one side upright to the other; in particular in the event of a side impact on an upright so as to transmit the energy due to the impact of this upright to the other and thus limit the deformation of the reinforcement. In addition, in the event of impact, the sheaths 40 or the rods of the head restraint bear against the fold 42, which prevents a sudden movement of the head restraint and thus prevents the passenger from suffering a "blow from the rabbit ". The ply 42 therefore makes it possible in particular to respond satisfactorily to the “whiplash” test of the Euro NCAP standard.

When the seat is mounted, a headrest 18 is mounted on the upper crosspiece 6 passing through the orifices passing through the upper 32 and lower 34 sides of the upper crosspiece 6. More particularly, the rods of the headrest 18 are for example mounted in sleeves 40 themselves received in the through holes so that the headrest 18 is adjustable in height by moving the rods in the sleeves 40.

Thus, the rods of the headrest and the sheaths 40 extend facing the upper 36 and lower 38 walls of the upper crosspiece, which increases the contact surface between the rods and the upper crosspiece 6 in the event of impact. and improves the behavior of the backrest in the event of a frontal impact on the vehicle.

Conventionally, a foam body is for example mounted on the frame 1 to form the backrest of the seat after the assembly of the frame 1.

As indicated above, the reinforcement 1 according to the invention 1 exhibits particularly satisfactory behavior in the event of an impact on the vehicle. More specifically, the reinforcement can respond satisfactorily to the "far side" and "whiplash" tests of the Euro NCAP standard. Thus, the frame makes it possible to protect a user of the seat in the event of an impact and to guarantee appropriate deployment of an airbag mounted on the frame 1 without deformation of the frame carrying the airbag.

Claims (14)

Seat back frame (1) comprising at least two side uprights (2) each extending between a lower edge (14) and an upper edge (16) in a direction of elevation, at least one lower crossbar (4) extending in a transverse direction substantially perpendicular to the direction of elevation, said lower crosspiece (4) joining the two side uprights (2) in the vicinity of the lower edges (14) of said side uprights (2), and at least one crosspiece upper (6) extending in the transverse direction and joining the two side uprights (2) in the vicinity of the upper edges (16) of the said side uprights (2), characterized in that the lower crosspiece (4) comprises at least one rib transverse (27) extending without interruption from one transverse end of the lower crosspiece (4) to the other transverse end. Backrest frame according to Claim 1, in which at least the lower crosspiece (4) comprises at least two projecting zones (29) extending respectively opposite each lateral upright (2), each projecting zone (29) the lower crosspiece (4) being welded to the side upright (2) extending opposite said projecting zone (29). Backrest frame according to Claim 1 or 2, in which each lateral upright (2) comprises at least one first upper projection (22) extending in the transverse direction in the vicinity of the upper edge (16) and facing the upper crosspiece (6), the upper crosspiece (6) being welded at least to the first upper projections (22) of the two side uprights (2). Backrest frame according to Claim 3, in which each side upright (2) comprises at least one main wall (8) extending in the direction of elevation and in a longitudinal direction substantially perpendicular to the direction of elevation and to the transverse direction, a first transverse flank (10) and a second transverse flank (12), the first transverse flank (10) and the second transverse flank (12) extending on either side of the main wall (8) in the direction of elevation and in the transverse direction, the lower crosspiece (4) being fixed to the first lateral flank (10) and the first upper projection (22) extending from the second lateral flank (12). Backrest frame according to Claim 4, in which the side uprights (2) each further comprise a second upper projection (24) extending in the transverse direction from the first side flank (10) of each side upright (2) in the vicinity of the upper edge (16) and opposite the upper crosspiece (6), said upper crosspiece (6) being further welded to the second upper projections (24). Backrest frame according to any one of Claims 2 to 5, in which the two projecting zones (29) of the lower crosspiece (4) each extend at a transverse end of the lower crosspiece, each projecting zone (29 ) extending in the direction of elevation above said transverse end, each transverse end and each projecting zone (29) being welded to a side post (2). Backrest frame according to any one of Claims 1 to 6, in which the upper crossbar (6) comprises a profile comprising a main wall (30) extending in the direction of elevation and the transverse direction, an upper flank ( 32) and a lower side (34) extending on either side of the main wall (30) in planes substantially perpendicular to the main wall (30), the upper side (32) extending above of the lower side (34) in the direction of elevation. Backrest frame according to Claim 7 when dependent on Claim 3, in which the main wall (30) is welded to the first upper projections (22) of the two side uprights (2). Backrest frame according to Claim 7 or 8, in which the upper flank (32) and the lower flank (34) each comprise at least one through hole for the passage of a headrest rod, the through orifice of the upper side (32) extending opposite the through hole of the lower side (34) in the direction of elevation. A backrest frame according to any of claims 7 to 9, wherein the top rail (6) comprises at least one top wall (36) extending in the elevation direction and the transverse direction from and above of the upper flank (32) in the direction of elevation, the main wall (30) and upper wall (36) extending on either side of the upper flank (32) in a longitudinal direction substantially perpendicular to the direction of elevation and transverse direction. A back frame according to claim 10, wherein the top wall (36) includes a transverse fold (42) extending seamlessly from one transverse end of the top wall (38) to the other. A backrest frame according to any one of claims 6 to 11, wherein the top rail (6) comprises at least one bottom wall (38) extending in the elevation direction and the transverse direction from and below of the lower side (34) in the direction of elevation, the main wall (30) and lower wall (38) extending on either side of the lower side (34) in a longitudinal direction substantially perpendicular to the direction of elevation and transverse direction. Backrest frame according to any one of Claims 1 to 12, in which the transverse rib (27) has a height, measured according to the direction of elevation, of between 10 mm and 25 mm and/or a depth, measured according to a longitudinal direction substantially perpendicular to the transverse direction and to the direction of elevation, greater than or equal to 3 mm. Vehicle seat comprising a backrest and a seat, the backrest comprising at least one frame (1) according to any one of claims 1 to 13, a body mounted on said frame (1) and a headrest (18) mounted on the upper crosspiece (6) of said reinforcement (1).