Axle for motor vehicle

Abstract

The invention relates to an axle (1) for a motor vehicle comprising a suspension arm (2, 3) and an axle head (9), said axle head (9) comprising a welded assembly of at least a first element (17) and a second element (18) welded to each other, the axle head comprising three orifices (10, 11, 12) which are each intended to receive a fastening element for fixing a wheel support element to said axle head (9); one of the orifices (10) being provided in a first fixing flange (13) and the other two orifices (11, 12) being provided in a second fixing flange (14), the first element (17, 34) comprising an arch (19) which projects above the suspension arm (2), the arch (19) comprising two uprights (20, 21) connected to each other and welded to said suspension arm (2);one of the first and second fixing flanges (14) being integrated into the second element (18), said second element (18) being supported and welded against each of the two uprights (20, 21) of the arch (19). Figure to be published with the abbreviation: Fig. 2;

Description

Title of the invention: Axle for motor vehicle

[0001] The invention relates to the field of motor vehicles.

[0002] The invention relates more specifically to an axle and in particular to a flexible axle of a motor vehicle.

[0003] A flexible axle, also called a deformable axle or semi-rigid axle, is a component commonly used in motor vehicles, particularly for the rear axles of passenger vehicles. The flexible axle is generally associated with coil springs and shock absorbers that work together to absorb shocks and maintain vehicle stability.

[0004] The flexible axle comprises two suspension arms, each connecting one of the rear wheels to the body, and a torsion beam connecting the two suspension arms to each other. Each suspension arm is equipped with an axle head welded to said suspension arm, which serves as a mounting point for a wheel bearing.

[0005] Prior art axle heads generally have four holes, each designed to receive a fastener for attaching the wheel bearing to the suspension arm. An axle equipped with such an axle head is not entirely satisfactory because it requires a large number of fasteners to attach each wheel bearing to the axle, resulting in significant weight and cost. However, in order to reduce carbon dioxide emissions from internal combustion engine vehicles or increase the range of electric vehicles, it is crucial to strive to make vehicle components as lightweight as possible.

[0006] Document FR3023215 discloses axle heads comprising a main part with three holes for the passage of fastening bolts and having a rounded upper part and a folded peripheral edge to increase its rigidity. Since the number of fastening bolts is limited to three per axle head, the mass and costs associated with the function of attaching the wheels to the axle are reduced. Furthermore, the folded peripheral edge increases the axle's rigidity, which allows for a reduction in the thickness of the sheet metal from which the axle is formed, and consequently, the axle's mass.

[0007] Such axle heads are not fully satisfactory because it would be desirable to lighten them even further without degrading their strength.

[0008] Also, a problem which arises and which the present invention aims to solve is to provide an axle offering an even better compromise between a reduced mass and a high rigidity, in order to guarantee adequate resistance to the stresses acting on the axle head.

[0009] In order to solve this problem, and according to a first object, an axle for a motor vehicle is proposed comprising a suspension arm and an axle head, said axle head comprising a welded assembly of at least a first element and a second element welded to each other, the axle head having three holes which are each intended to receive a fastening element for fixing a wheel support element to said axle head; one of the holes being provided in a first fixing flange and the other two holes being provided in a second fixing flange, the first element having an arch which projects above the suspension arm, the arch having two uprights connected to each other and welded to said suspension arm; one of the first and second fixing flanges being integrated into the second element, said second element being supported and welded against each of the two uprights of the arch.

[0010] Thus, by manufacturing the axle head from an assembly of at least two elements welded together rather than from a single, monolithic piece of material, the axle head can offer an even better compromise between reduced mass and high rigidity. Indeed, the use of several parts welded together, one of which forms an arch welded to the suspension arm and another of which forms a mounting flange, makes it possible to obtain an axle head with a more complex shape than if it were formed from a single piece, which allows it to better withstand mechanical stresses while reducing the amount of material used. In addition, each element of the axle head is optimized for its specific needs, which makes it possible to integrate reinforcements where they are necessary, while reducing the material in less stressed areas. Increased rigidity can thus be obtained in critical areas without adding weight to the overall axle head.

[0011] In addition, the number of fastening elements is limited to three per axle head, which reduces the mass and costs associated with the function of fastening the wheels to the axle.

[0012] According to embodiments, such an axle may include one or more of the following characteristics.

[0013] According to one embodiment, the wheel support member is a wheel bearing.

[0014] According to one embodiment, the arch further comprises a vault which connects the two uprights; the said vault having an upward convexity, so that the width of the arch decreases from bottom to top. This makes it possible to limit the width of the axle head and, consequently, to further limit its mass.

[0015] According to another embodiment, the arch comprises an upper part extending perpendicularly to the two uprights.

[0016] According to one embodiment, the uprights have, in their lower part, a landing edge which has a concavity in which the suspension arm is at less partially inserted and along which said docking edge is welded to the suspension arm.

[0017] According to one embodiment, the other of the first and second fixing flanges is made of material with the arch of the first element or formed by a third element which is welded to said first element.

[0018] According to one embodiment, the third element is supported and welded against each of the two uprights of the arch.

[0019] According to one embodiment, the first and second fixing flanges define bearing surfaces against which the wheel support member is intended to bear, directly or indirectly, the bearing surfaces extending in the same vertical plane.

[0020] According to one embodiment, the first and second mounting flanges are spaced vertically apart to create a central opening between them. This central opening further lightens the axle head.

[0021] According to one embodiment, the uprights have cutouts formed from an outer edge of the uprights between the first and second fixing flanges. The cutouts allow the axle head to be further lightened.

[0022] According to one embodiment, the first fixing flange is arranged above the second fixing flange.

[0023] According to one embodiment, the three openings consist of an upper opening and two lower openings, each having a center. The centers of the openings define an isosceles triangle. A median (M) of the triangle, passing through the center of the upper opening, is vertical and forms an axis of symmetry of the triangle. The upper opening is provided in the first mounting flange, and the lower openings are provided in the second mounting flange. This allows for balancing the forces exerted on the fasteners and the axle head.

[0024] According to one embodiment, the second fixing flange is integrated into the second element.

[0025] According to one embodiment, the second fixing flange is further welded directly to the suspension arm.

[0026] According to one embodiment, the second fixing flange has two lugs in which are respectively provided one and the other of the two orifices of the second fixing flange, the lugs being spaced apart from each other by a cut made in the upper edge of the second fixing flange.

[0027] According to one embodiment, the ears are respectively supported and welded against a contact surface of each of the two uprights.

[0028] According to one embodiment, the lugs each extend beyond the upright against which they rest. This facilitates welding operations. It also increases the dimensions of the bearing surface against which the support member rests, directly or indirectly, in order to better distribute the stresses, without increasing the dimensions and consequently the mass of the arch.

[0029] According to one embodiment, the second element comprises two lateral tabs, each folded from a lateral edge of the second mounting flange towards the suspension arm, and having a free end that is welded to said suspension arm. The two lateral tabs thus provide an additional support point and further reinforce the structure.

[0030] According to one embodiment, the second element comprises a lower tab folded from a lower edge of the second mounting flange towards the suspension arm and having a free end welded to said suspension arm. The lower tab thus provides an additional support point and further reinforces the structure.

[0031] According to one embodiment, the second element has an H shape with two arms connected by a bridge and is welded to the uprights along each of the two arms of said H. This allows for particularly long weld lines in order to improve the mechanical strength of the axle head, while limiting its mass.

[0032] According to one embodiment, the arms of the H extend beyond the uprights to facilitate welding operations.

[0033] According to one embodiment, said axle head comprises a welded assembly of the first element, the second element and a third element; the second fixing flange being integrated into the second element and the first fixing flange being integrated into the third element, said third element being supported and welded against each of the two uprights of the arch.

[0034] According to one embodiment, the median (M) is intended to pass through a geometric axis of rotation of the wheel.

[0035] According to one embodiment, the holes are provided above the suspension arm. This allows access to the inner face of the mounting surface for installing the nuts.

[0036] According to one embodiment, the axle further comprises a wheel bearing and three fixing members which each pass through one of three holes in the mounting flange and which fix the wheel bearing to the axle head.

[0037] According to one embodiment, the fastening elements are bolts, each comprising: - a threaded screw that passes through a hole in a flange of the wheel bearing and through one of the holes in the axle head; and - a nut which is mounted on said threaded screw.

[0038] According to one embodiment, the threaded screw has a diameter between 10 and 14 mm. This helps to ensure satisfactory resistance of the three fasteners.

[0039] According to one embodiment, the threaded screw has a yield strength greater than or equal to 900 MPa. This also contributes to the reliability of the fastening.

[0040] According to one embodiment, the threaded screw has a tensile strength greater than or equal to 1040 MPa. This also contributes to the reliability of the fastening.

[0041] According to one embodiment, the axle comprises two suspension arms which are connected to each other by a cross member and two axle heads of the aforementioned type which are respectively welded to one and the other of the two suspension arms.

[0042] Other features and advantages of the invention will become apparent from the following description of particular embodiments of the invention, given by way of example but not limitation, with reference to the accompanying drawings in which:

[0043] [Fig-1] is a top view of a rear flexible axle of a motor vehicle.

[0044] [Fig.2] is a partial perspective view of an axle showing an axle head and its attachment to a suspension arm according to a first embodiment.

[0045] [Fig.3] is a side view of the suspension arm and axle head according to the first embodiment of [Fig.2].

[0046] [Fig.4] is a rear view of the suspension arm and axle head according to the first embodiment of Figures 2 and 3.

[0047] [Fig.5] is a partial perspective view of an axle showing a suspension arm and an axle head according to a second embodiment.

[0048] [Fig.6] is a side view of the suspension arm and axle head according to the second embodiment of [Fig.5].

[0049] [Fig.7] is a rear view of the suspension arm and axle head according to the second embodiment of Figures 5 and 6.

[0050] [Fig.8] is a schematic side view of an axle head according to a third embodiment.

[0051] [Fig.9] is a perspective view of an axle head according to a fourth embodiment, not covered by the claims.

[0052] The orientations expressed in the description are given with reference to an orthonormal XYZ frame, shown in the figures, in which X represents the longitudinal direction, oriented from the front to the rear of the vehicle, Y the transverse direction oriented towards the right of the vehicle, and Z the vertical direction oriented towards the top of the vehicle in its usual position, i.e. resting on its wheels.

[0053] Fig. 1 represents a flexible axle 1 of a rear axle of a motor vehicle. It has an H-shaped structure.

[0054] The axle 1 comprises two suspension arms 2, 3. One end of each suspension arm 2, 3, namely its front end 4, is articulated to the vehicle body via a flexible joint 5. Such a flexible joint 5 comprises, for example, an elastomer bushing mounted radially between two metal bushings. It thus allows limited rotation of the suspension arms 2, 3 relative to the body while filtering vibrations and shocks.

[0055] The suspension arms 2, 3 are connected to each other by a cross member 6. In the embodiment shown, the cross member 6 and the suspension arms 2, 3 are made of steel tubes that are welded together or obtained from stamped blanks and then welded. The cross member 6 is capable of torsional deformation, particularly when the vehicle encounters irregularities in the road, which allows for limited relative movement of the rear wheels with respect to each other. This improves driving comfort by reducing the impact of bumps and potholes.

[0056] Each suspension arm 2, 3 is equipped with a suspension cup 7 which is welded to said suspension arm 2, 3 and which supports one end of one of the suspension springs 8. Each suspension arm 2, 3 is also equipped with a mounting bracket, not shown, to which is attached one end of a suspension damper, also not shown.

[0057] Each of the suspension arms 2, 3 is also equipped with an axle head 9, a first embodiment of which is shown in figures 2 to 4. The axle head 9 is intended to ensure the attachment, to said suspension arm 2, 3, of a wheel bearing and a braking device.

[0058] The wheel bearings are advantageously of the third generation. Such wheel bearings integrate the wheel bearing and the hub into a single compact unit. Furthermore, one of the wheel bearing rings is equipped with a flange having holes for the passage of fasteners used to secure the wheel bearing and the stator, i.e., the stationary part, of the braking device to the axle head 9. The other wheel bearing ring is equipped with a flange for securing the rim and the rotor, i.e., the moving part, of the braking device.

[0059] The axle head 9 is made of metal, preferably steel, and is attached and welded to the suspension arm 2, at a rear end of said suspension arm 2.

[0060] As shown in Figures 2 and 3, the axle head 9 has only three openings, namely one upper opening 10 and two lower openings 11, 12. The three openings 10, 11, 12 are intended to receive the fasteners for fixing the wheel bearing to the axle head 9.

[0061] The fasteners are, for example, bolts. Such bolts have a screw equipped with a threaded shank that passes, on the one hand, through a hole in a flange of the wheel bearing and, on the other hand, through one of the holes 10, 11, 12 of the axle head 9. A nut is screwed onto the threaded shank and bears against the inner face of the axle head 9. The bolts are, for example, of type M10, M12, or M14, that is, they have a metric thread and their screw has a diameter of 10, 12, or 14 mm. The screws preferably have a yield strength greater than or equal to 900 MPa and a tensile strength greater than or equal to 1040 MPa.

[0062] The three openings 10, 11, 12 are provided above the part of the suspension arm 2 to which said axle head 9 is attached, which facilitates access to the nuts.

[0063] The centers of the three holes 10, 11, and 12 define a triangle oriented so that one of its vertices points upwards. The median M passing through the vertex of the triangle, namely the center of the upper hole 10, is therefore oriented vertically. Furthermore, the median M advantageously passes through the geometric axis of rotation of the wheel. In addition, the triangle is an isosceles triangle, so the distance between the center of the upper hole 10 and that of one of the lower holes 11 is equal to the distance between the center of the upper hole and that of the other lower hole 12. The median M passing through the upper hole 10 thus forms an axis of symmetry of the triangle. This makes it possible to balance the forces acting on the fasteners and on the axle head 9.

[0064] The axle head 9 has two mounting flanges 13, 14 in which the openings 10, 11, 12 are provided. The mounting flanges 13, 14 define bearing surfaces 15, 16 against which the bearing is intended to bear, either directly or indirectly, for example via the stator of the braking device. As illustrated in [Fig. 4], the bearing surfaces 15, 16 extend in the same vertical plane, thus ensuring a uniform distribution of the forces exerted on the bearing.

[0065] The axle head 9 is not formed in one piece. Thus, in the first embodiment of Figures 2 to 4, it consists of a welded assembly of two separate elements, namely a first element 17 and a second element 18. The first element 17 and the second element 18 are welded to each other and are furthermore each welded to the suspension arm 2.

[0066] The first element 17 comprises an arch 19 which projects upwards above the suspension arm 2. The thickness direction of the arch 19, that is to say, the direction extending perpendicularly to its curvature and consequently along the direction transverse Y, extends perpendicularly to the bearing surfaces 15, 16 of the axle head 9.

[0067] The arch 19 comprises two uprights 20, 21 and a vault 22 that connects the two uprights 20, 21. The vault 22 has an upward convexity, so that the width of the arch 19 decreases from bottom to top. Each of the uprights 20, 21 has, in its lower part, a buttress edge 23 that has a concavity complementary to the convexity of the suspension arm 2. This concavity allows a portion of the cross-section of the suspension arm 2 to interlock with the buttress edge 23 of the uprights 20, 21. The interlocking between the buttress edge 23 and the suspension arm 2 is vertical, that is to say, the buttress edge 23 is positioned on each side, internal and external, of the suspension arm 2.

[0068] The uprights 20, 21 are welded to the suspension arm 2 along said concavity of the docking edge 23, for example by arc welding.

[0069] In the embodiment shown, the section of the suspension arm 2 has a flat 24, visible on the [Fig.4], oriented towards the inside of the suspension arm 2 and against which is welded a part of the abutment edges 23 of the uprights 20, 21 of the arch 19.

[0070] The fixing flange 13 in which the upper orifice 10 is provided is integrated into the first element 17. In other words, said fixing flange 13 is formed in one piece, that is to say, is made of material, with the arch 19. It extends downwards from the top of the arch 19.

[0071] The first element 17 is, for example, produced by molding or by stamping.

[0072] The mounting flange 14 in which the lower openings 11, 12 are provided is integrated into the second element 18. The fixing flanges 13, 14 are spaced apart in the vertical direction, which allows for a central opening 25 to lighten the axle head 9.

[0073] The mounting flange 14 has two lugs 26, 27 formed on either side of the median M of the triangle and in which are respectively formed one and the other of the lower orifices 11, 12. The lugs 26, 27 are spaced from each other by a cutout 28 formed in the upper edge of the mounting flange 14. The cutout 28 makes it possible to further lighten the axle head 9 and advantageously has a rounded shape, which limits the concentrations of stresses.

[0074] The ears 26, 27 are respectively in contact with one and the other of the two uprights 20, 21. In addition, the second element 18 is welded to the first element 17 along the support of the ears 26, 27 against the contact surfaces of the uprights.

[0075] In order to limit the amount of material of the arch 19 and consequently its mass, the uprights 20, 21 have cutouts 29, 30 made from the outer edge of the uprights 20, 21 between the two fixing flanges 13, 14.

[0076] The lower openings 11, 12 are positioned such that their axis passes inside the arch 19. Furthermore, the lugs 26, 27 each extend beyond the upright 20, 21 against which they rest. In other words, the forwardmost lug 26 projects forward beyond the upright 20 against which it rests, while the rearmost lug 27 projects backward beyond the upright 20 against which it rests. This facilitates welding operations.

[0077] According to an advantageous embodiment, the second element 18 is welded to the first element 17 along the support of the ears 26, 27 against the uprights 20, 21.

[0078] Furthermore, the second element 18 comprises three tabs 31, 32, 33 by which it is welded to the suspension arm 2, namely a lower tab 31, and two lateral tabs 32, 33. The two lateral tabs 32, 33 are folded perpendicularly to the bearing surface 16 of the mounting flange 14, from either of the two lateral edges of the mounting flange 14 towards the suspension arm 2. The free end of each of the lateral tabs 32, 33 is welded to the suspension arm 2. To this end, as shown in [Fig. 4], said free end advantageously has a concavity complementary to the convexity of the suspension arm 2.

[0079] Furthermore, as illustrated in [Fig.4], the lower tab 31 is folded from a lower edge of the fixing flange 14, towards the suspension arm 2 and the free end of said lower tab 31 is welded to the suspension arm 2.

[0080] The second element 18 is, for example, produced by stamping or bending.

[0081] With reference to Figures 5, 6 and 7, an axle head 9 is observed according to a second embodiment. This embodiment differs in particular from that described above with reference to Figures 2 to 4 in that the axle head 9 consists of a welded assembly of three separate elements, namely a first element 34, a second element 35 and a third element 36.

[0082] The arch 19 and the mounting flange 13 are not integrated into the same element as in the previous embodiment but belong respectively to the first element 34 and the third element 36. Furthermore, the second element 35, which incorporates the mounting flange 14, is not welded directly to the suspension arm 2 and is welded to it only via the first element 34. The second element 35 and the third element 36 consist of the metal plates that are welded to the arch 19 and form the mounting flanges 14 and 13 respectively.

[0083] As in the previous embodiment, each of the uprights 20, 21 of the arch 19 has, in its lower part, a landing edge 23 which has a concavity complementary to the convexity of the suspension arm 2, which allows the section of the suspension arm 2 to fit together with the lower end of the uprights 20, 21. However, as illustrated in [Fig.7], in this embodiment, the fit between the landing edge 23 and the suspension arm 2 is lateral, that is to say that the landing edge 23 is positioned above and below the suspension arm 2. The uprights 20, 21 are also welded to the suspension arm 2 along said landing edge 23.

[0084] The second element 35 consists of a flat metal plate in which the lower openings 12, 13 are provided and which forms the fixing flange 14. As in the previous embodiment, the fixing flange 14 has two lugs 26, 27 which are spaced apart by a cutout 28. The lugs 26, 27 are respectively supported and welded against a contact surface of each of the two uprights 20, 21. In the embodiment shown, the second element 35 has an H shape and is welded to the uprights 20, 21 along each of the two arms of said H.

[0085] Furthermore, the third element 36 consists of a flat metal plate in which the upper opening 10 is formed and which forms the fixing flange 14. The metal plate bears against a contact surface of the arch 22 of the arch 19 and against contact surfaces of the uprights 20, 21. The third element 36 is also welded to the arch 19 along said contact surfaces. The third element 36 extends beyond said contact surfaces.

[0086] The first element 35, the second element 35 and the third element 36 are, for example, made by cutting or machining a sheet of metal and then bending or stamping the sheet metal. They each have a thickness of between 4 and 8 mm, for example on the order of 6 mm.

[0087] Figure 8 schematically represents an axle head according to a third embodiment. As in the embodiment described previously with reference to Figures 5 to 7, the axle head 9 consists of a welded assembly of three separate elements 34, 35, 36, the first, second, and third elements 34, 35, 36 forming, respectively, the arch 19, the mounting flange 14, and the mounting flange 13. However, in this embodiment, the arch 19 has a different shape since its upper part extends perpendicularly to its two uprights 20, 21. In addition, the second element 35 has a lower tab 31 by which it is also welded directly to the suspension arm 2.

[0088] Figure 9 illustrates an axle head 9 according to a fourth embodiment, which is not covered by the claims. As in the embodiments described above, the bearing 37 is fixed by means of three fastening members passing through three holes 10, 11, 12. However, only the upper hole 10 is provided in the head axle 9. The two lower orifices 11, 12 are directly provided in the suspension arm 2. The two lower orifices 11, 12 receive threaded inserts 38, 39 which are fixed in said lower orifices 11, 12 and are intended to receive the fixing screws of the bearing 37.

[0089] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention, as defined by the claims.

[0090] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those stated in a claim.

[0091] In the claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

Demands

1. Axle (1) for a motor vehicle comprising a suspension arm (2, 3) and an axle head (9), said axle head (9) comprising a welded assembly of at least a first element (17, 34) and a second element (18, 35) welded to each other, the axle head comprising three holes (10, 11, 12) which are each intended to receive a fastener for attaching a wheel support element to said axle head (9); one of the orifices (10) being provided in a first fixing flange (13) and the other two orifices (11, 12) being provided in a second fixing flange (14), the first element (17, 34) comprising an arch (19) which projects above the suspension arm (2), the arch (19) comprising two uprights (20, 21) connected to each other and welded to said suspension arm (2);one of the first and second fixing flanges (14) being integrated into the second element (18, 35), said second element (18, 35) being supported and welded against each of the two uprights (20, 21) of the arch (19).;

2. Axle according to claim 1, wherein the other of the first and second fixing flanges (13) is made of material with the arch (19) of the first element (17) or formed by a third element (36) which is welded to said first element (34).

3. Axle according to claim 1 or 2, wherein the first fixing flange (13) and the second fixing flange (14) are spaced apart from each other in a vertical direction so as to provide a central opening (25) between the first and second fixing flanges (13, 14).

4. Axle according to claim 3, wherein the uprights (20, 21) have cutouts (29, 30) formed from an external edge of the uprights (20, 21) between the first and second fixing flanges (13, 14).

5. Axle according to claims 1 to 4, wherein the three openings consist of an upper opening (10) and two lower openings (11, 12), each having a center, the centers of the openings defining an isosceles triangle, a median (M) of the triangle passing through the center of the upper opening (10) being vertical and forming an axis of symmetry of the triangle, the upper opening (10) being provided in the first mounting flange (13) and the openings lower (11, 12) being provided in the second fixing flange (14).

6. Axle according to any one of claims 1 to 4, wherein the second fixing flange (14) is integrated into the second element (18,35).

7. Axle according to claim 6, wherein the second fixing flange (14) has two lugs (26, 67) in which are respectively provided one and the other of the two orifices (11, 12) of the second fixing flange (14), the lugs (26, 67) being spaced apart from each other by a cutout (28) provided in the upper edge of the second fixing flange (14).

8. Axle according to claim 7, wherein the ears (26, 27) are respectively supported and welded against a contact surface of each of the two uprights (20, 21).

9. Axle according to any one of claims 6 to 8, wherein the second element (18) has two lateral tabs (32, 33) which are each folded from a lateral edge of the second fixing flange (14) towards the suspension arm (2) and which have a free end which is welded to said suspension arm (2).

10. Axle according to any one of claims 6 to 9, wherein the second element (18) has a lower tab (31) folded from a lower edge of the second fixing flange (14) towards the suspension arm (2) and having a free end welded to said suspension arm (2).

11. Axle according to claim 6 or 7, wherein the second element (35) has an H shape with two arms connected by a bridge and is welded to the uprights (20, 21) along each of the two arms of said H.

12. Axle (1) according to any one of claims 1 to 11, wherein said axle head (9) comprises a welded assembly of the first element (34), the second element (35) and a third element (36); the second fixing flange (14) being integrated into the second element (35) and the first fixing flange (13) being integrated into the third element (36), said third element (36) being supported and welded against each of the two uprights (20, 21) of the arch (19).

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