EP3773078B1

EP3773078B1 - Seating furniture support arrangement

Info

Publication number: EP3773078B1
Application number: EP19785797.2A
Authority: EP
Inventors: Sebastian Svensson
Original assignee: Inter Ikea Systems BV
Current assignee: Inter Ikea Systems BV
Priority date: 2018-04-11
Filing date: 2019-03-04
Publication date: 2024-07-31
Anticipated expiration: 2039-03-04
Also published as: CN112118771A; EP3773078A1; WO2019199216A1; EP3773078A4

Description

Field of technology

The present invention relates to a seating furniture support arrangement for a seat or a backrest.

Background

Seating furniture support arrangements for seats or backrests based on structures with longitudinal beams are known in the prior art (e.g. in FR2587201 A1 ). The support may be for example be provided by sheets stretched between the longitudinal beams. Such pieces of furniture may be designed to be assembled by persons not specially trained for the task at the point of future use.
There is always a need to improve such seating furniture support arrangements.

Summary

To this end, the invention provides a seating furniture support arrangement for a seat or a backrest, as claimed in claim 1 and a method of assembling a piece of seating furniture as claimed in claim 14. Preferred features are set out in the dependent claims.

Brief description of the drawings

Figs 1A, 1B, and 1C are perspective views of a sofa support arrangement according to the prior art.
Fig. 2A shows a perspective view, close-up cross-sectional view, and close-up perspective view of a sofa with the support arrangement according to the present inventive concept in an initial position.
Fig. 2B shows a perspective view, close-up cross-sectional view, and close-up perspective view of a sofa with the stretching member of the support arrangement pivoting in an intermediate position.
Fig. 2C is a close-up cross-sectional view with the stretching member of the support arrangement pivoting at a position corresponding to the point of maximum tension.
Fig. 2D is a perspective view, close-up cross-sectional view, and close-up perspective view of a sofa with the stretching member of the support arrangement in final position, with the elastic sheets stretched.
Fig. 3 shows a perspective view of a sofa with the support arrangement in final position, with the elastic sheets stretched, illustrating seat and backrest pillows being added to complete the sofa.
Fig. 4 is a cross-sectional view showing an alternative embodiment where the stretching member is separate from the first longitudinal beam.
Figs 5A and 5B are perspective exploded views of a transverse stretcher.
Fig. 6 is a perspective view of the assembled transverse stretcher.
Figs 7A and 7B are perspective views and Figs 7C and 7D are cross sectional views showing the sequence of mounting the transverse stretcher between two longitudinal beams of a sofa.
Figs 8A-8C are perspective views showing the mounting sequence of a sofa equipped with the transverse stretcher.

Detailed description

Fig. 1 shows an arrangement according to the prior art. A sofa 102 frame comprises a first short-end section 104a, a second short-end section 104b and a support arrangement 106 comprising a first longitudinal beam 108, a second longitudinal beam 110, and a third longitudinal beam 112, all beams running between the first short-end section 104a and the second short-end section 104b. A first sheet 114 may be stretched between the first longitudinal beam 108 and the second longitudinal beam 110 and a second sheet 116 may be stretched between the first longitudinal beam 108 and the third longitudinal beam 112 forming, respectively, a support for a seat and for a backrest. The seat and/or backrest may be formed by placing pillows on the sheets 114, 116. For stretching the sheets, there is a stretching mechanism 118: the first longitudinal beam may be manually pulled and fixed with a screw 120.
Fig 2A-2D show a seating furniture support arrangement 6 according to the present inventive concept. In this specific embodiment, the seating furniture support arrangement 6 is for a sofa 2, however, the arrangement is equally suitable for other pieces of seating furniture, such as an armchair.
With reference to Fig. 2A, a sofa 2 comprises a frame comprising a first short-end section 4a, a second short-end section 4b and the support arrangement 6. The support arrangement 6 comprises a first longitudinal beam 8, a second longitudinal beam 12, and a third longitudinal beam 10.
The first longitudinal beam 8, the second longitudinal beam 12 and the third longitudinal beam 10 may be provided in a kit and mounted to the first short-end section 4a and the second short-end section 4b at the site of use of the sofa. As depicted in Fig. 2A they are each mounted between the first short-end section 4a and the second short-end section 4b. A first elastic sheet 14 is attached to the first longitudinal beam 8 and the second longitudinal beam 12 and a second elastic sheet 16 is attached to the first longitudinal beam 8 and the third longitudinal beam 10.
The second longitudinal beam 12 and the third longitudinal beam 10 are fixed with respect to the first short-end section 4a and the second short-end section 4b, while the first longitudinal beam 8 is pivotable, through plates 20, about a pivot axis running between a first pivot point P on the first short-end section 4a and a corresponding second pivot point on the second short-end section 4b. A lever 18, functioning as a handle, adapted to aid pivoting of the first longitudinal beam 8, is fixed to the first longitudinal beam 8 at a midpoint between the first short-end section 4a and the second short-end section 4b of the frame. Other locations for a lever or handle, as well at a different number of handles are equally possible, or no handle at all with an external force or torque provided through different means.
In embodiments where the stretching member is separate from the first longitudinal beam 8, as discussed in conjunction with Fig. 4 below, the handle 8 or lever will be located on the stretching member. Preferably, the handle is removable, for example by being screw-mountable on the first longitudinal beam 8. In that case, the lever 18 may be threaded as to be screw-mounted in a corresponding threaded bore in the first longitudinal beam 8 to be easily mountable before use and dismountable after use. Alternatively, the lever 18 may be foldable into or against the first longitudinal beam 8 after use.
Again with reference to Fig. 2A, a cross-sectional view of the area close to the first pivot point P shows the longitudinal beam 8, the lever 18, the first sheet 14 and the second sheet 16. The sheets 14, 16 attach to the first longitudinal beam 8 at an attachment point 26 which is rotatable with respect to the longitudinal beam 8.
In the present embodiment, an elastic sheet folds around the first longitudinal beam 8 forming a pocket, which is closed by a seam at the attachment point 26. The elastic sheet in the form of the pocket is rotatable with respect to the first longitudinal beam 8. In this configuration, the first elastic sheet 14 and the second elastic sheet 16 may be part of the same elastic sheet.
A vertical, or close to vertical, plate 20 is fixed with respect to the first longitudinal beam 8 close to the first short-end section 4a of the frame. The plate has a slot 22 configured to interact with a stop on the first short-end section of the frame in the form of a pin 24. An identical plate 20 configured to interact with an identical tap (not visible) in the second short-end section 4b located close to the second short-end section 4b of the frame. The plates 20, and thereby the first longitudinal beam 8, are pivotable around the first pivot point P and the second pivot point (not visible) respectively.
The first longitudinal beam 8, the lever 18, and the plates 20 provide a mechanism for, during assembly of the sofa, stretching the first elastic sheet 14 between the first longitudinal beam 8 and the second longitudinal beam 12, and further for stretching the second elastic sheet 16 between the first longitudinal beam 8 and the third longitudinal beam 10, where first longitudinal beam 8 functions as a stretching member for the elastic sheets, as will be described below.
In the cross-sectional view of Fig. 2A, a circular arc L1 shows the path traveled by the slot 22 of the plate 20 when the first longitudinal beam 8 pivots around the pivot point P. Similarly, a second circular arc L2 shows the path traveled by the center of the first longitudinal beam 8 during the same pivoting movement. Thus, the first elastic sheet 14 is, with the sofa seating furniture support arrangement 6 in installed position, connected to the stretching member, which in this embodiment is identical to the first longitudinal beam 8, in such a way that the first longitudinal beam 8 pivoting with respect to the frame, in response to an application of an external force or torque, stretches the first elastic sheet 14.Fig. 2B shows the same arrangement as in Fig. 2A during pivoting of the first longitudinal beam 8, the pivoting motion being driven by the application of an external force on the lever 18, as shown with large straight arrows. During pivoting, shown with small curved arrows, the distance between the attachment point 26 and the second longitudinal beam 12 will increase, thereby starting to stretch the first elastic sheet 14. The tension force of the first elastic sheet 14, shown with a large straight arrow next to the first elastic sheet 14 in the cross-sectional view, will counteract the pivoting movement, as its leverage with respect to the pivot point P is opposite to that of the externally applied force. Thus, the external force applied to the lever 18 will need to work against the tension force of the first elastic sheet 14. Since the attachment point 26 is rotatable with respect to the first longitudinal beam 8, the tension force of the first elastic sheet 14 will cause the attachment point 26 to move around the first longitudinal beam 8 so that the stretched first elastic sheet 14 is perpendicular to the surface of the first longitudinal beam 8. The path followed by the attachment point 26 at this stage of pivoting will be determined by this condition.
In alternative embodiments (not shown) the attachment point 26 may instead be fixed with respect to the first longitudinal beam 8 and the plates 20, i.e., to the stretching member. In this case the attachment point 26 will during pivoting follow a circular path similar to L1 or L2.
In the shown embodiment, the first longitudinal beam 8 has a circular cross-section. However, other alternatives such a rectangular or elliptic cross-section are possible. The longitudinal beam 8 may either be fixed with respect to the plates 20, resulting in an attachment point 26 fixed with respect to the plates 20, or be pivoted at the plates 20 at a point offset from the first pivot points P and the second pivot point.
With the pivoting motion continuing, the external force applied to the lever 18 will continue to work against the tension force of the first elastic sheet 14, with the length of the lever arm of the tension force with respect to the pivot point P decreasing, and the tension force increasing, until a point, i.e., position, of maximum tension force is reached, as shown in a cross-sectional view in Fig. 2C. Here, with the first elastic sheet 14 crossing the pivot point P, the lever arm of the tension force of the first elastic sheet 14 has been reduced to zero, thus applying no torque with respect to the pivot point P.
With further pivoting movement driven by the externally applied force on the lever 18, the lever arm of the tension force of the first elastic sheet 14 will produce a torque around the pivot point P of opposite sign compared to the situation before the pivoting movement reached the position of maximum tension, thus resulting in a torque working in the same direction as the externally applied force on the lever 18. Thus, the tension force of the first elastic sheet 14 will from now on facilitate the pivoting until the slot 22 of the plate 20 has reached the stop in the form of the pin 21, as shown in Fig. 2D.
Thus, the torque provided by the external force on the lever 18, works against the torque provided by the tension force of the first elastic sheet 14 until the position maximum tension is reached, as depicted in Fig. 2C, past which position of maximum tension the tension force of the first elastic sheet 14 instead facilitates further pivoting of the first longitudinal beam 8, acting to keep the stretching member in place its final position, as depicted in Fig. 2D.
Through the leverage made possible, the mechanism is easy to operate even when having a high tension in the elastic sheets, providing good rigidity to the support.
The elastic sheets 14, 16 need to be elastic enough to be able to be brought to the position of maximum tension. However, in general, a large degree of elasticity is not required in the elastic sheets, i.e., their coefficient of elasticity, defined as the ratio of tension force to degree of stretching, may be rather high. For a given geometry of the stretching member, a higher coefficient of elasticity allows for a high degree of tension of the sheet, giving rigid support for the seat och backrest.
Optionally, a latch (not shown) may be provided to prevent the first longitudinal beam 8 from sliding back from the final position, for example due to an externally applied force.
In the embodiment shown in Figs 2A-2D, the second elastic sheet 16 and the distance between the attachment point 26 and the third longitudinal beam 10 are arranged so that the second elastic sheet remains slack during the pivoting movement up to the position of maximum tension (Fig. 2C) of the first elastic sheet 14, only being stretched after that point. Thus, in this embodiment, during pivoting, the external force works against the tension force of the first elastic sheet up to the position of maximum tension, with the second elastic sheet only being stretched with the pivoting having passed the position of maximum tension. In this way, the tension force of one of the first elastic sheet 14 helps to stretch the second elastic sheet 16 past the position of maximum tension, with the effect of less external force being needed to pivot the stretching member up to that point. With both the first elastic sheet 14 and the second elastic sheet 16 being stretched, the position of the attachment point 26, being rotatable around the first longitudinal beam 8, will be determined by the condition that the vector sum of the tension force of the first elastic sheet 14 and the tension force of the second elastic sheet 16 is perpendicular to the surface of the first elastic beam 8.
In an alternative embodiment (not shown) both the first elastic sheet 14 and the second elastic sheet 16 are stretched simultaneously up to the position of maximum tension. In that case, the position of maximum tension will be defined based on the vector sum of the tension force of the first elastic sheet 14 and the tension force of the second elastic sheet 16. As a further alternative, there may be only one elastic sheet, either for providing support for the seat or for the backrest.
Fig. 4 shows an alternative embodiment, in a cross-sectional view, where the first longitudinal beam 8 is separate from the mechanism 28 for stretching the first elastic sheet 14 and fixed to the frame. As in the embodiments described in conjunction with Figs 2A-2D above, the elastic sheet 14 runs between the second longitudinal beam (not shown) and the first longitudinal beam 8. However, instead from being fixed at the first longitudinal beam, it now continues to the separate stretching mechanism 28. In the depicted embodiment, the first elastic sheet 14 lies on top of the first longitudinal beam 8. However, other arrangements, such as the first elastic sheet 14 running through a slot or opening in the first longitudinal beam 8, are equally possible. The stretching mechanism 28 operates according to the same principle as described above in conjunction with Figs 2A-2D. In the depicted embodiment, the first elastic sheet 14 attached to a cylindrical structure similar to the first longitudinal beam depicted in Figs 2A-2D, however, this structure, to which the elastic sheet 14, is fixed, may in this embodiment be smaller, as it does not carry the load of, for example, an occupant of the sofa. In this embodiment, all other structures may be identical to what was described above in conjunction with Figs 2A-2D.
Finally, Fig. 3 shows the sofa 2 where the first elastic sheet 14 and the second elastic sheet 16 have been stretched according to the procedure described above. With the stretched first elastic sheet 14 now providing support for the seats of the sofa, pillows 54 may be added, as indicated with arrows, to complete the sofa seats. Likewise, with the second elastic sheet 16 now providing support for the backrest of the sofa, pillows 52 may be added to complete the backrest.
Figs 5A and 5B are exploded views showing a transverse stretcher 500 from two different angles. The stretcher 500 comprises a front part 502 and a back part 504, each having a quadratic cross section. They are joined at a hinge 520. The transverse stretcher 500 is intended to be mounted between the first longitudinal beam 8 and the second longitudinal beam 12 of a sofa, as described in the following.
At its front end, the front part 502 has a tap 506 designed to mate with a corresponding hole 704 in the second longitudinal beam 12 (cf. Figs 7A and 7B). The tap 506 is surrounded by a collar 507 with a shape matching that of the second longitudinal beam 12.
Similarly, at its back end, the back part 504 has a tap 508 designed to mate with a corresponding hole 702 in the first longitudinal beam 8 (cf. Figs 7A and 7B). The tap 508 is surrounded by a collar 509 with a shape matching that of the first longitudinal beam 8.
For the hinge 520, the front part 502 has at its back end protrusions 522 which extend through holes 514 in a cap 518 having a U-shaped cross section. A bolt 510 may be used to lock the hinge. Before the bolt 510 is applied and tightened, the front part 502 and the back part 504 are free to pivot against each other by means of the hinge 520, limited by a surface 516 of the front part 502 being stopped by the inner surface corresponding to the lower part of the "U" of the U-shaped profile of the cap 518.
The hinge 520 may be locked by inserting and tightening the bolt 510 from the side of the back part 504, where the bolt 510 extends through a hole 511 in the cap 518, through the inner surface of the cap 518 and into a threaded hole 512 on the surface 516 of the front part 502, locking the hinge 520 and the surface 516 of the front part 502 against the inner surface of the cap 518 of the back part 504. Fig. 6 shows the transverse stretcher 500 thus assembled and locked. The stretcher 500 has a slightly bent shape, forming a smooth arc, which with the stretcher in installed position extends in a downward direction with respect to the sofa 2 (cf. Figs 8A-8C).
Figs 7A and 7B are perspective views and Figs 7C and 7D are cross sectional views showing the sequence of mounting the transverse stretcher 500 between the first longitudinal beam 8 and the second longitudinal beam 12 of the sofa 2 (cf. Figs 8A-8C). The transverse stretcher 500 may be installed on piece of furniture with a pivotable first longitudinal beam 8, as will be described in conjunction with the sofa 2 of Figs 8A-8C below, or on a piece of furniture, such as a sofa, having fixed longitudinal beams, for example having the arrangement described in conjunction with Fig. 4 above.
Firstly, with reference to Fig. 7A, and in particular in the enlarged area of that figure, the tap 508 of the back part 504 of the transverse stretcher 500 is brought into the corresponding hole 702 of the first longitudinal beam 8. The bolt 510 has been inserted, but not tightened, so that there is play in the hinge 520.
Then, with reference to Fig. 7B, the tap 506 of the front part 502 is brought into the vicinity of, or in contact with, the corresponding hole 704 of the second longitudinal beam 12, possibly by wiggling the transverse stretcher 500 as shown by a double arrow. The resulting configuration is shown in cross section in Fig. 7C. As can be seen, the fact that the bolt 510 has not yet been tightened results in the play that allowed the transverse stretcher 500 to be inserted as just described.
Now, with reference to Fig. 7D, tightening the bolt 510, as shown by a circular arrow, causes the front part 502 and the back part 504 of the transverse stretcher 500 to move as indicated by straight arrows, while the taps 506, 508 are pushed into their respective longitudinal beams 8, 12 and the collars 507, 509 are pushed against their respective longitudinal beams 8, 12. The transverse stretcher 500 is now locked in place in mounted position.
Figs 8A-8C are perspective views showing the mounting sequence of a sofa 2 equipped with a support arrangement 6 comprising the transverse stretcher 500. The sofa is similar to the one discussed above in conjunctions with Figs 2A-2D and all features and alternatives discussed there are applicable to this sofa 2, except for the differences discussed in the following.
With reference to Fig. 8A, the sofa 2 comprises a frame comprising a first short end section 4a and a second short end section 4b and a seating support arrangement 6 comprising a first longitudinal beam 8, a second longitudinal beam 12 and a third longitudinal beam 10. A first elastic sheet 14 is stretchable between the first longitudinal beam 8 and the second longitudinal beam 12, forming support for the seat of the sofa, and a second elastic sheet 16 is optionally stretchable between the first longitudinal beam 8 and the third longitudinal beam 10. The first longitudinal beam 8 is pivotable at the first short end section 4a and the second short end section 4b, forming a pivot axis, for stretching the first elastic sheet 6, and optionally the second elastic sheet 16, according to the same principle as described in conjunction with Figs 2A-2D.
With reference to Fig. 8B, a user may, during assembly of the sofa 2, apply an external force or torque on the lever 18, for stretching the first elastic sheet 14 and optionally the second elastic sheet 16. Different from what was described in conjunction with Figs 2A-2D, stretching occurs when the first longitudinal beam 8 pivots in a stretching direction that is opposite to what was described in conjunction with Figs 2A-2D , with the front side, with respect to the sofa, of the first longitudinal beam 8 moving downwards and the back side moving upwards. This allows the transverse stretcher 500 (cf. Fig. 8C) to act on the first longitudinal beam 8 in the stretching direction. The stretching direction is indicated by a circular arrow. The stretching of the first elastic sheet 14 is indicated by two straight arrows. At each of its ends, the first longitudinal beam 8 has a vertical plate 20 which eventually reaches a stop 24. After stretching, the lever 18 may be removed by the user.
Finally, with reference to Fig. 8C, the transverse stretcher 500 may be installed as described in conjunction with Figs 7A-7D above. With the hole 702 (cf. Fig. 7A) located offset to the pivot axis of the first longitudinal beam 8, the transverse stretcher 500 acts in the stretching direction on the first longitudinal beam 8, locking it in place in its final position.
The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

A seating furniture support arrangement (6) for a seat, comprising:
a first (8) and a second (12) longitudinal beam, each being mountable to a seating furniture frame comprising one or more parts;

a transverse stretcher (500) mountable between said first longitudinal beam (8) and said second longitudinal beam (12);

an elastic sheet (14) for providing support for said seat; and

a mechanism for stretching said elastic sheet (14) between said first longitudinal beam (8) and said second longitudinal beam (12) through pivoting of said first longitudinal beam (8), with respect to said frame, in a stretching direction, in response to an application of an external force or torque, wherein said first longitudinal beam (8) is pivotable on said frame around a pivot axis and said stretcher (500) in mounted position locks said first longitudinal beam (8), and thereby said mechanism for stretching said elastic sheet, in place in a final position with respect to said pivoting, with said elastic sheet (14) stretched,

characterized in that said elastic sheet (14), with said seating furniture support arrangement (6) in installed position, is connected to said first longitudinal beam (8) in such a way that in said pivoting of said first longitudinal beam (8) for stretching said elastic sheet (14), said external force or torque works against the tension force of said elastic sheet (14) until a point of maximum tension is reached, past which point of maximum tension said tension force facilitates further pivoting of said first longitudinal beam (8), acting to keep said first longitudinal beam (8) in place in said final position.
The seating furniture support arrangement (6) of claim 1, wherein said transverse stretcher (500) in mounted position locks said first longitudinal beam (8) in place in said final position by pushing on said first longitudinal beam (8) in said stretching direction at a point offset to said pivot axis.
The seating furniture support arrangement (6) of any one of the preceding claims, wherein said transverse stretcher (500) at each end has pins which, with said transverse stretcher (500) in mounted position, fit with holes (702, 704) on said first longitudinal beam (8) and said second longitudinal beam (12) for mounting said transverse stretcher.
The seating furniture support arrangement (6) of any one of the preceding claims, said transverse stretcher (500) comprising two parts (502, 504) connected at a hinge (520), said hinge (520) being lockable for locking said transverse stretcher (500) in mounted position.
The seating furniture support arrangement (6) of any one of the preceding claims, wherein said elastic sheet (16; 14) is a first elastic sheet (14) and said seating furniture support arrangement further comprises:
a third longitudinal beam (10); and

a second elastic sheet (16) for providing support for a backrest, said second elastic sheet (16) also being connected to said first longitudinal beam (8), so that said pivoting of said first longitudinal beam (8) also stretches said second elastic sheet (16) between said first longitudinal beam (8) and said third longitudinal beam (10).
The seating furniture support arrangement (6) of claim 5, wherein said external force or torque works against the tension force of one of said first elastic sheet (16; 14) and said second elastic sheet (14; 16) up to said point of maximum tension, the other of said first elastic sheet and said second elastic sheet only being stretched with said pivoting having passed said point of maximum tension.
The seating furniture support arrangement (6) of claim 5, wherein said external force or torque works against the tension forces of both said first elastic sheet (16; 14) and said second elastic sheet (14; 16) up to said point of maximum tension.
The seating furniture support arrangement (6) of any one of claims 1-7, wherein said elastic sheet (16; 14), with said seating furniture support arrangement (6) in installed position, folds around said first longitudinal beam (8) forming a pocket, said pocket preferably being closed by a seam (26).
The seating furniture support arrangement (6) of any one of claims 1-8, further comprising a lever (18) for applying said external force or torque for pivoting said first longitudinal beam (8), said lever preferably being removable or foldable after use.
The seating furniture support arrangement (6) of any one of claims 3-9, further comprising a stop (24), against which stop (24) said tension force of said elastic sheet (14) acts through said first longitudinal beam (8) to keep said first longitudinal beam (8) in place in said final position.
The seating furniture support arrangement (6) of any one of claims 1-10, further comprising a latch further acting to lock said first longitudinal beam (8) in place in said final position.
A piece of seating furniture (2) comprising the seating furniture support arrangement (6) of any one of the preceding claims.
A kit for assembling a piece of seating furniture comprising the seating furniture support arrangement (6) of any one of claims 1-11.
A method of assembling a piece of seating furniture, comprising:
providing:
a seating furniture frame in one or more parts (4a, 4b);

a first longitudinal beam (8) and a second longitudinal beam (12), each attached to said seating furniture frame; and

an elastic sheet (14) for providing support for a seat or a backrest;

stretching said elastic sheet (14) between said first longitudinal beam (8) and said second longitudinal beam (12) by pivoting said first longitudinal beam (8) with respect to said frame, bringing said first longitudinal beam (8) to a final position with respect to said pivoting;

locking said first longitudinal beam (8) in said final position by mounting a transverse stretcher (500) between said first longitudinal beam (8) and said second longitudinal beam (12), and
connecting said elastic sheet (14), with said seating furniture support arrangement (6) in installed position, to said first longitudinal beam (8) in such a way that in said pivoting of said first longitudinal beam (8) for stretching said elastic sheet (14), said external force or torque works against the tension force of said elastic sheet (14) until a point of maximum tension is reached, past which point of maximum tension said tension force facilitates further pivoting of said first longitudinal beam (8), acting to keep said first longitudinal beam (8) in place in said final position.