WO1999015390A1

WO1999015390A1 - Method for manufacturing a tubular sheet metal beam having corbelled-out end sections and a sheet metal beam manufactured in accordance with the method

Info

Publication number: WO1999015390A1
Application number: PCT/SE1998/001691
Authority: WO
Inventors: Anders Sundgren; Mats Lindberg; Göran Berglund
Original assignee: Accra Teknik Ab
Priority date: 1997-09-23
Filing date: 1998-09-22
Publication date: 1999-04-01
Also published as: AU9289298A; SE508235C2; SE9703422D0; SE9703422L

Abstract

The present invention refers to a procedure for manufacturing a tubular sheet metal beam having corbelled-out end sections, preferably intended to form part of a vehicle body, and a sheet metal beam manufactured according to the procedure. To simplify and cut the cost of manufacturing stiffened, tube-shaped beams with corbelled-out end sections for welding, it is suggested according to the invention that the beam is partly or wholly provided with concertina-like wave-shaped profiles (9) with a series of alternating valleys (10) and peaks (11) running in the longitudinal direction of the beam and that these wave-shaped profiles form an excess of material that is used in a subsequent corbelling-out operation of the end sections (12) of the beam.

Description

Method for manufacturing a tubular sheet metal beam having corbelled-out end sections and a sheet metal beam manufactured in accordance with the method .

The present invention refers to a procedure for manufacturing a tubular sheet metal beam having corbelled-out end sections, preferably intended to form part of a vehicle body, and a sheet metal beam manufactured according to the procedure.

Beams included in vehicle bodies commonly include sheet metal that has been bent, profiled or shaped by some other suitable means into halves that are joined together to form box-like elements that have flanged or corbelled-out sections arranged at their ends so that they can be joined to adjoining elements by, for example, spot welding. Besides permitting spot welding, the said corbelled-out end sections of the beam also have the task of reducing notch effects and the occurrence of concentrated areas of tension in the transition sections of the beams by having a larger radius of transition at the point of joining.

Since it is very important from a point of view of fuel economy and for other reasons to reduce the weight of a vehicle as much as practically possible, it is desirable to design all load-bearing beams included in a vehicle body so that an optimal relationship is obtained between their own weight and their ability to take up loads (stiffness in flexing) and their disposition to buckling due to the effect of external forces. With regard to beams used in the construction of roofs, it is desirable for reasons of cabin space, among other things, to always keep the height of the space between the outer and inner roof panels of the body of the vehicle as small as possible, which is why this space constitutes a limitation from a design point of view, and thus why the load-bearing elements that are included in the roof construction are not allowed to have an outer dimension that is too large. Known box-shaped beam-like elements can have a variety of cross-sectional shapes but have commonly been given elongated profiles and bends to gain an increased volume and thereby an increased ability to accommodate loads as well as to hinder buckling and being pressed inwards, in other words, to avoid a deformed or reduced cross-section that would, for example, cause the beam to collapse due to the effect of external forces such as running into wild animals or if the vehicle rolls over.

One disadvantage of the production technology of beams known to date is that they must be cut open at their ends to allow the ends to be corbelled-out, which naturally means an additional cost in production.

A wish to be able to simplify and cut the cost of manufacturing stiffened, tube- shaped beams for vehicle bodies produced from sheet metal has therefore existed for some time. These beams should have corbelled-out end sections for welding and one present objective is thus to achieve a procedure that realises this goal and, more specifically expressed, that permits a procedure for a significantly simplified production of tubular-shaped sheet metal beams that display a high degree of stiffness in relation to their weight, at the same time as they are very resistant to buckling forces, and that can be provided in a very simple way with the essential shape preparation required at the end sections for joining together with adjoining beams.

These objectives are achieved by the procedure and the sheet metal beams obtained using it having the features specified in the characteristics of the claims.

The invention is described in more detail below with reference to the enclosed illustrations where; fig. 1 shows schematically by a cut-away diagram how a section of a vehicle body is built-up and how a beam according to the invention is used in the body, fig. 2 shows a perspective view of a beam manufactured according to the principles of the invention, fig. 3 shows the beam according to fig. 2 in a corbelled-out embodiment, and fig. 4 shows a cross-section through the beam. That generally designated 1 in fig. 1 includes a roof construction that is part of the vehicle body and includes a tubular-shaped sheet metal beam 2 that has been formed in agreement with the principles of the present invention and that, more specifically, is arranged to extend between side sections 3, 4 (only partly shown in the figure) arranged on either side of the body in the form of the commonly referred to A, B and C posts. The sheet metal beam according to the invention could naturally be located at any suitable position in the body 1 , but in the embodiment shown here, it forms a cross-ways roof beam whose primary task is to bring rigidity to the body and to prevent the roof from being pressed inwards if the vehicle rolls over.

As is evident from figs. 2 and 4, the beam is formed from joined together pieces of sheet metal with a thin-walled, enclosed trapezium-shaped cross-section that includes two flange sections 5, 6 separated at a distance from one another and parallel with the main plane of the beam, plus two rib sections 7, 8 at right angles to the flange sections. The thickness of the sheet metal in this described embodiment of the beam has been chosen to be in the range 0.4 - 0.5 mm and the other dimensions of the beam chosen are 22 mm height and 58 mm width. The span of the beam (its length) is not specified in detail. The material is some type of steel that can be hardened, preferably carbonised manganese steel such as drilling steel or similar. The pieces of sheet metal include a first and a second similarly U-shaped cross-sectional profile formed by rolling i.e. in the form of shanks and a central section, that are turned to face each other and joined together by welding so that they together form the enclosed, box-shaped beam mentioned above. Since welding in general reduces the resistance of the material in a negative manner in the vicinity of the point of welding, the welded joints are situated on those parts that are intended to form the principle plane of the beam 2, in other words, in what is known as the neutral plane that is free from tension when the beam is subjected to stress.

To stiffen the beam 2, those parts that take up the greatest tension during the application of a force to the beam so that they are subjected to a bending movement, i.e. primarily those parts that, according to the orientation of the beam, form the flange sections of the beam, are arranged with a certain excess of material in the form of concertina-like, trapezium-shaped wave profiles 9 running in the longitudinal direction of the flange sections with a series of alternating valleys 10 and peaks 11. As this excess of material is located at the greatest possible distance from a centre of gravity that coincides with the main plane of the beam, a large moment of inertia (I) is obtained and thereby also a large resistance to bending (W) for the beam. This wave-shaped excess of material also significantly increases the ability of the beam to withstand buckling, as should be realised.

It should also be pointed out that this profiling does not necessarily need to be trapezium-shaped, as shown here, but can also have other suitable shapes, such as, for example, the shape of a sine wave. In the described embodiment of the invention, the height of the concertina-like, wave-profiles, i.e. the distance between the valley 10 and peak 11, is selected to be 2.2 mm, which in this case is equivalent to about 10% of the height of the beam. The concertina-like, wave-profiling 9, when based on that known as flat thin plate sheet metal, is preferably produced by roller moulding in a rolling press, whereby the U-shaped shanks of the starting blanks are also arranged in the same manufacturing operation.

In contrast to the flange sections 5, 6 of the beam 2, the rib sections 7, 8 are not given a longitudinal wave-shaped form as such a form, at least in this described embodiment of the invention, would only act as a deformation notch and as such would exclusively weaken the beam 2 when seen in the intended direction of its bending.

It is, however, worth considering stiffening the beam 2 and giving it further loading capacity in the direction of bending by providing the rib sections with local indentations in the cross-sectional direction of the sheet metal element (not shown in the figures), i.e. indentations that extend vertically towards the main plane of the beam. In such a case, these indentations could be advantageously produced already in the roller moulding process for the U- shaped halves by arranging the pair of rollers that is part of the roller mill to be used for producing the profiles by means of interacting elevations and recesses.

Fig. 3 shows how the beam 2 is arranged prior to a welding operation by the end sections 12 of the beam having been given the necessary corbelling-out or flanging 13 by means of suitable shaping tools such as a die and counter die. According to the principles of the invention, this corbelling-out operation utilises the excess material that is formed from the concertina-like wave profiles 9. It is advantageous if this excess material is so adapted that the corbelled-out wave-shaped sections (flange sections 5, 6) maintain a primarily flat surface in the corbelled-out position. During the corbelling-out operation of the beam 2 shown here, rib sections 7, 8 formed from shanks located on either side of the centre of the beam are initially pressed outwards, as indicated by the arrows in fig. 3, so that the upper and lower flange sections 5, 6 seen in the above figure are hereby spread outwards to a certain extent and the rib sections attain the desired angle against the beam 2 or point in essentially opposite directions out from this. Following this, the now essentially extended respective flange sections 5, 6 of the beam 2 are pressed outwards and backwards in an opposite direction, i.e. so that they attain an angle primarily at right angles to the main plane of the beam 2.

It should be realised that the present invention is not limited to that described above and shown in the figures, but can be altered and modified in many different ways within the scope of the concept of the invention specified in the following claims. For example, the beam according to the invention need not necessarily have the shaped profile in the example of the embodiment shown and described here, but can naturally have any shaped profile whatsoever that is suitable for the purpose.

Claims

1. Procedure for manufacturing a tubular sheet metal beam having corbelled-out end sections, preferably intended to form part of a vehicle body characterised in that the beam is partly or wholly provided with concertina-like wave-shaped profiles (9) with a series of alternating valleys (10) and peaks (11) mnning in the longitudinal direction of the beam and that these wave-shaped profiles form an excess of material that is used in a subsequent corbelling-out operation of the end sections (12) of the beam.

2. Procedure according to claim 1 characterised in that the beam is produced from two or more sheet metal elements that are joined together so that they define rib sections (7, 8) and flange sections (5, 6) of the beam with respect to the orientation of the beam in use and that the wave-shaped profiles (9) are arranged in those sections of the sheet metal element that form the flange sections (5, 6) of the beam in the joined-together sheet metal element.

3. Procedure according to claim 2 characterised in that the beam is produced from a first and a second sheet metal element essentially U-shaped in cross-section, in other words, in the form of shanks and a middle section where the wave-shaped profiles (9) are arranged on the middle section, whereby the U-shaped elements, when facing one another, are welded together to form one beam and that the welded joints are situated to coincide with the main plane of the beam.

4. Procedure according to claims 2-3 characterised in that the sheet metal element is formed by an essentially flat form of that known as a thin metal plate being fed through a rolling press with interacting pairs of rollers.

5. Procedure according to any of the previous claims characterised in that material that can be hardened is used as starting material for the beam (2) and that the vehicle body produced is hardened in a subsequent hardening operation.

6. Tubular sheet metal beam having corbelled-out end sections, preferably intended to form part of a vehicle body characterised in that the beam (2) is partly or wholly provided with concertina-like wave-shaped profiles (9) with a series of alternating valleys (10) and peaks (11) running in the longitudinal direction of the beam and that these wave-shaped profiles form an excess of material that is suitable for a subsequent corbelling-out operation of the end sections (12) of the beam.

7. Tubular sheet metal beam according to claim ╧îcharacterised in that it includes two or more sheet metal elements that are joined together so that they define rib sections (7, 8) and flange sections (5, 6) of the beam with respect to the orientation of the beam in use and that the wave-shaped profiles (9) are arranged in those sections of the sheet metal element that form the flange sections of the beam.

8. Tubular sheet metal beam according to claim ╧îcharacterised in that it includes a first and a second sheet metal element essentially U-shaped in cross-section, in other words, in the form of shanks and a middle section, that are welded together to form a box-like beam whereby the wave-shaped profiles are arranged on the middle section of the U-shaped sheet metal element.

9. Tubular sheet metal beam according to any of claims 6-7 characterised in that it is made of a metal that can be hardened and that it is hardened.