The present invention relates to a profile beam of closed profile form for joining together bodywork parts.

A lorry cabin is made up of a number of bodywork parts, namely a front part, a rear piece, side pieces and also floor and roof panels.

In order to obtain a strong cabin which satisfies the strict requirements relating to the safety both of the driver and of the passenger in a collision or in another near-accident, each bodywork part is reinforced on its side facing the coupέ area with beams of closed profile form.

When the various bodywork parts are to be joined together to each other in order to form a cabin, it is desirable, for reasons of production engineering, to connect the beams of each bodywork part to each other by means of spot-welding connections, so that they form a stable cabin frame.

However, the spot-welding is incompatible with the desire to be able to use prefabricated beams of closed profile form, since, when beams of this type are used, it is not possible to gain access to all the joints which are to be spot-welded. In order to join the beams to each other, it is in fact necessary to gain access with the spot-welding tool inside the beams, but this is not possible because the beams are closed.

In known solutions, use is therefore made of beams with a so-called hat-profile form, which are each designed with an elongate opening. When joining the beams together, the opening is used in order to gain access to the joint between two beams in the cabin. After the spot- welding operation, the elongate opening is covered with

a covering panel which is spot-welded to the hat beam, thus resulting in a beam with a closed profile form.

The known solutions have a number of disadvantages, of which it may be mentioned that it is time-consuming and relatively difficult, in automated assembly, to position and spot-weld the elongate covering panels to the respec¬ tive beam inside the relatively narrow cabin. This disadvantage is particularly marked in automated assemb¬ ly, since a robot carrying out the automated assembly is, for production-engineering reasons, positioned outside the cabin and designed with a working arm extending in through the relatively narrow door or window openings of the cabin.

The present invention aims to eliminate the said disad- vantages of the known solutions and therefore relates to a profile beam which can be used in automated assembly and welding of a cabin frame. To this end, the invention is characterised by the fact that the profile beam at at least at its one end section is designed with a foldable cover element which can be folded between a first posi¬ tion and a second position, in that the foldable cover element in the first position exposes an opening in the closed form of the profile beam in order to permit access with tools for joining together the profile beam to another bodywork part, and in that the foldable cover element in the second position covers the opening and a joint made upon joining together.

With the profile beam according to the invention it is possible to satisfy simultaneously the previously incom- patible desires on the one hand to use profile beams of closed profile form and on the other hand to spot-weld such profile beams to each other or to other bodywork parts.

The present invention also relates to a method for joining together bodywork parts. The method according to

the invention is characterised in that a cover element formed on the profile beam of the first bodywork part is made to turn from a first position, in which the cover element has exposed an opening for access with tools to the area for joining together, to a second position, in which the cover element covers the joint, and in that the cover element is thereafter spot-welded to the profile beams.

The method according to the invention permits a relative- ly simple and quick assembly of cabin parts to each other, despite the small cabin space available during the assembly operation. The method also means that the assembly can be carried out to a great extent automati¬ cally and with the aid of robots, both for the assembly itself and for the welding together.

Other features characterising the invention will emerge from the subsequent patent claims and from the following description of an embodiment exemplifying the invention, in which description reference is made to the attached figures, in which

Figure 1 shows a diagrammatic side view of a vehicle cabin.

Figure 2 shows diagrammatically a rear view of a vehicle cabin, Figure 3 shows a profile beam according to the invention, and

Figure 4 shows a joint between two profile beams.

Figures 1 and 2 show a vehicle cabin 2 with a coupe space 1. The vehicle cabin 2 is intended for a heavy vehicle such as a lorry and is arranged upon a conventional (and therefore not shown) underframe which constitutes part of a vehicle chassis.

The cabin 2 is provided with a cabin floor 3 separating the coupe area 1 from the vehicle chassis. The cabin floor 3 is connected at its rear to a vertical cabin wall

4 ^" delimiting the coupe area 1 at the back, and, at its front, to an essentially vertical front 5 delimiting the coupδ area 1 at the front. The cabin wall 4 and the front

5 are connected to each other by means of a roof 6 and by means of side walls 7, 8 arranged on either side of the vehicle cabin.

The floor 3 and the rear wall 4, front 5, roof 6 and side walls 7, 8 are made of pressed plate. In order to satisfy the requirements relating to the safety both of the driver and passenger in a collision or in another near- accident, each pressed plate 3-8 is reinforced on its side facing the coupέ area 1 with elongate profile beams 12 of closed profile form. In this connection, the profile beams 12 on each pressed plate 3-8 are connected to each other and form a framework. The broken lines in Figures 1 and 2 indicate some of the beams 12 in the framework.

In order to connect the various elongate profile beams on each plate 3-8 to each other, and, when assembling the cabin 2, in order to join the profile beams 12 of the different pressed plates 3-8 to each other in such a way that they together form a stable cabin frame, use is made of profile beams 12 ^' according to the invention.

A number of profile beams 12 ^" according to the invention are included in the cabin 2. However, in order to clearly illustrate the present invention, only one of these beams is described, namely a profile beam 12 ^* arranged on the side wall 7 for connecting the framework of the side plate 7 to the framework of the rear cabin wall 4. In this respect it is understood that the other profile beams included in the framework are designed in principle in a similar manner.

Figure 3 shows a profile beam 12 ^' according to the inven¬ tion. The beam 12 ^' consists of a prefabricated profile beam made up of two halves of pressed plate welded

together to each other. One of the halves consists of an elongate beam with, in this example, a so-called hat profile form, to which there has been securely welded an elongate cover element 17 constituting the other half, so that a beam 12' of a closed profile form has been ob¬ tained. At the end sections of the beam 12', the elongate cover element 17 is designed with at least one, but in this exemplary embodiment two, slots 18 extending in the transverse direction of the beam 12 ^' . The ends of the cover element 17, hereinafter referred to as cover elements 16, are not securely welded to the hat profile form prior to assembly, but instead can be folded by means of the presence of the slots between a first and a second position. In the figure the cover elements 16 are shown in the folded-out position.

In order to illustrate a joint between two profile beams. Figure 4 shows a joint marked by A in Figures 1 and 2 in one rear corner of the cabin. In this connection it is assumed that one of the beams is of the design described above, for which reason previously used reference numbers are again used for this beam 12 ^' .

A profile beam 12 ^" on the rear wall of the cabin is lesigned at its one end with two essentially parallel and horizontal securing plates 20, 21 extending essentially in the forward direction of the vehicle. The securing plates 20, 21 are shown in Figure 1. The securing plate 20, 21 extend into the profile beam 12 ^' , each securing plate 20, 21 being spot-welded to the upper or lower side surfaces respectively of the profile beam 12' with four welding points 24.

It is of course not necessary to design the one profile beam with securing plates which are overlapped by the other profile beam, but instead it is also advantageous¬ ly possible to arrange the profile beams essentially in line with one another and to let the end section of one profile beam surround the end section of the other

profile beam. This is possible since the profile beams are made of relatively thin plate and are therefore sufficiently flexible in order to permit joining together, despite the fact that the beams themselves have identical dimensions in a cross-section.

Figure 4 also shows that the elongate cover element 17 is designed with slots 18 along which the foldable cover element 16 can be folded. The foldable cover element 16 is shown with full lines in a first position, in which it exposes an area for joining together between the profile beam 12' of the side wall and the profile beam 12" of the rear wall, and with a broken line 16 ^' in a second position in which it covers the joint and the area for joining together.

The method according to the invention is initiated by a bodywork part 7, on which a profile beam 12' according to the invention is mounted or securely welded upon assembly of the cabin 2, being positioned in such a way that it partially surrounds a profile beam 12" mounted on another bodywork part 4 and defines an area for joining together between the profile beams 12', 12". Thereafter, a spot- welding tool mounted on a robot is guided in through the opening which the cover element 16 exposes, after which the profile beams 12 ^' , 12" are spot-welded to each other in the area for joining together and there define a joint. Thereafter, the cover element 16 is made to turn, manually or by means of the robot, from the first posi¬ tion, in which it has exposed the area for joining together, to the second position, in which it covers the joint. A robot 22 is shown diagrammatically in Figure 3. The robot 22 comprises a working head 25, which is rotatable between a spot-welding position and a position pushing on the cover element 16. After the cover element 16 has been folded so that it covers the joint, the cover element 16 is spot-welded, by means of the robot-mounted spot-welding tool, to the profile beam 12' and/or the profile beam 12".

The invention should not be regarded as being limited to the embodiment described, but instead can be modified in a number of alternative embodiments within the scope of the following patent claims.