The structure of a railway vehicle for transporting passengers can be described in simple terms as a box beam or car shell with self-carrying capability, comprising an underframe (1), roof (2), sideframes (3), a head (4) and a frontframe (5) (see figure 1). There are also other substructures and components with specific structural functions.

The sides have a structural function comparable with the web of a beam in which the floor and roof are the chords.

The side is therefore subjected essentially to shear and compression stresses which are mainly borne by the covering plates of the car shell-face plates. With the objective of complementing the structural function of the covering and to avoid the occurrence of instability therein, there is a substructure of vertical and horizontal beams known as posts (6) and rails (7) respectively.

In order to guarantee the structural continuity of this substructure of posts and rails, it is necessary to use special components. To date this function has been carried out by a set of shear plates-"gussets"- (8) and when necessary brackets welded to the mounting posts and spacers in the zone of interception (see figure 2).

By altering the profiles of the posts and rails from U-shaped to Q- shaped, it is possible to use a connecting component with a more involving shape which is therefore able to transmit the stress more uniformly between the posts and the rails. This is how the cruciform joint was developed, the shape of which can be considered as a fusion of two perpendicular Q-shaped profiles.

Thus, an objective of the invention is to design a connecting component which makes it possible to transmit stress uniformly by guaranteeing the continuity of the substructure formed from posts and rails.

The use of this new connecting element called a cruciform joint offers substantial advantages over the process that was previously used.

One of the main advantages of the use of cruciform joint is the more uniform transfer of stress between the posts and rails, which is a result of the greater envelopment of the components to be joined.

Owing to the enveloping form of the cruciform joint it is possible to use them as a positioning element and support for the posts and rails during assembly, thus making it possible to develop a new philosophy for assembling the sides of the vehicle body. This philosophy is based on the division of each side into subsets, panels, forming a new generation of extremely flexible figs.

In these models the panels are assembled, fixing in place the cruciform joint, posts and rails by means of supports and clamps which in turn are positioned in a rigid structure by means of moveable connectors. This makes it possible to rapidly transform the assembly line of one type of vehicle into another, and guaranteeing that the subsets will have accurate dimensions.

By using these models, the easy and accurate positioning of the components of the panels in their correct positions reduces manufacturing time and improves the quality of the final product.

In the same way it is possible to standardise the positioning of the welding points in the connection between the cruciform joints, posts and rails.

The use of standard connecting components that are easy to differentiate between submodels also facilitates the management of project materials.

To give a better understanding of the description hereunder, a sheet of drawings is attached hereto by way of a non-restrictive example and shows the following: Figure 1 shows the structure of a railway vehicle for passenger transport; Figure 2 shows a post/rail connection by means of"gussets" ; Figure 3 is a perspective view of the connecting element known as a cruciform joint; Figure 4 is a perspective view seen from the other side of the cruciform joint shown in the previous figure; Figure 5 shows the application of the cruciform joint in order to connect the mounting posts/spacers; Figure 6 shows a"half Cluzeta''-cruciform joint Figure 7 shows the application of the"half Cluzeta''-cluciform joint represented in the previous figure; Figures 8 and 9 show two variations on the basic form of the cruciform joint; Figure 10 shows part of the structure of a side panel mounted with the aid of cruciform joints; As shown in the figures, the cruciform joints (9) have two different zones. Round the edges they comprise four sections with a Q-shaped cross- section (10) the dimensions of which are designed to fit correctly onto the posts (6) and rails (7), and a central zone, the core (11), where the adjacent Q-shaped profiles are joined (see figure 3). In the core (11) there may be two holes (12) designed to position the cruciform joint on the assembly model. In some specific cases only a"half Cruzeta"-cruciform joint is used (13), as shown in figure 7.

In some cases the spacing between the posts needs to be reduced, thus making it necessary to develop a few variations on the length of the section of the cruciform joints with the Q-shaped profile (14) in relation to the basic form shown in figure 3, leaving the core (11) unaltered. Also, in order to allow cables to pass through the mounting posts and rails it is necessary in some cases to provide slits (15) for this purpose in the centre of the sections of the cruciform joints with the Q-shaped profile (figures 8 and 9).

Despite these variations, the manufacturing method is common to all the cruciform joints and the necessary differentiation is obtained during a complementary phase.

The cruciform joints for current applications is obtained by means of cold deep drawing AISI 301LN or 304L stainless steel with a thickness of 1.3 mm. However, other materials and thicknesses can be used depending on the requirements of the project.

The variations in the lengths and slits of the Q-shaped sections can be obtained using complete cruciform joints, thus reducing the number of tools necessary for producing them. Finally, the cruciform joints are mounted onto the rest of the structure using resistance spot welding, although it is possible to use other joining methods using laser welding. The standardisation of the joining method using cruciform joints facilitates robotise assembly and optimises the use of robotised resistance or laser welding. The structural homogeneity obtained can be observed in figure 10.

For the development, optimisation and certification of the use of the cruciform joints, various analyses were carried out using the finite elements method and static and fatigue tests on submodels of a side panel. By means of these analyses the final form of the cruciform joint was determined, as well as the method of joining it to the other components, in order to guarantee that there is no reduction in the overall rigidity of the side panels built using cruciform joints as opposed to the conventional method of joining using shear plates.

The present invention should not be limited by the embodiments described above, which were only given by way of non-restrictive example.

Thus, other variations can be made to the connecting element, which will be obvious to persons skilled in the art. The invention must only be limited by the following claims.