Abstract:
Vehicle rollover protection system with a roll bar, whose top piece is rounded in a U-shape. Such top pieces are typically tubular and are made from pipe bending parts. In order to achieve a three-dimensional contour of the top piece with irregular cross section of its profile, the invention calls for at least the tubular top piece consisting of at least two axially divided partially tubular shells of sheet metal, joined to each other and having different geometrical shapes according to a nominal contour.

Description:
FIELD OF THE INVENTION 
   The invention refers to a vehicle rollover protection system with a roll bar, whose top piece is tubular and rounded in a U-shape. 
   Such rollover protection systems serve to protect the passengers of motor vehicles without a protective roof, typically in convertibles or sports cars with a cover, since the vehicle will roll over on the roll bar. 
   BACKGROUND OF THE INVENTION 
   It is known how to provide a permanently installed roll bar spanning the entire width of the vehicle. In this solution, the increased air drag and the occurrence of driving noises is perceived as a drawback, apart from affecting the appearance of the vehicle. 
   It is also known how to coordinate a permanently installed, i.e., rigid U-shaped roll bar of unchangeable height with each vehicle seat. This solution is typically used in sports cars to underscore the sporty appearance. 
   Widely used in convertibles are structural solutions in which the U-shaped roll bar is retracted in the normal condition, and in case of danger, i.e., an imminent rollover, it is quickly extended into a protecting position, in order to prevent the passengers from being crushed by the vehicle rolling over. 
   These rollover protection systems typically have a U-shaped roll bar arranged in a guide body fixed to the vehicle, or a roll bar formed from a profile body, while the guide body is secured in a case housing. This roll bar or roll body in the normal state is held down in a position of rest by a holding device against the pre-stress force of an activating compression spring, and in event of a rollover a sensor releases the holding device and the force of the compression spring brings it into an upper protecting position, while a locking device which is then activated prevents the roll bar from being retracted or pushed in. Typically one case is assigned to each vehicle seat, especially for the rear seats. Alternatively, two cases can also be integrated in a rear wall structural unit. 
   One such case design for a roll bar system with a U-shaped roll bar is shown by DE 43 42 400 A 1. 
   The invention starts both from over-roll protection systems with rigidly installed roll bar and also those with deployable U-shaped roll bar, yet it also comprises systems in which only the top piece of the roll bar, formed from a profiled body, for example, is rounded in a U-shape. 
   U-shaped roll bars are today typically fabricated from simple pipe bending parts, with a rounded top piece and two parallel leg pieces. Such a U-shaped roll bar can be bent into a U-shape from a single piece of steel or aluminum tubing, or it can consist of a tubular and U-shaped top piece, to which the leg tubes are welded. In such a three-piece roll bar, the top piece can also be connected to the leg tubes by screwing, gluing, or a form-fitted connection (e.g., DE 202 15 276 U1). The U-shaped top piece can advantageously be made from a different material than the leg tubes. 
   U-shaped roll bars, and especially rigid roll bars, which are permanently arranged to be visible in the vehicle, are subject increasingly to safety engineering and also design-oriented requirements. The result is roll bars which, due to the necessary shape, and necessary length and cross section, are no longer fabricated as simple pipe bending parts. These requirements demand a three-dimensional bar contour with irregular cross section of the bar profile. As part of the safety engineering, there can be greatly rounded and flattened segments near the head of the vehicle passengers, so as to minimize the severity of an injury by the thickest possible foam padding. 
   SUMMARY OF THE INVENTION 
   The basic problem of the invention is to configure the above-indicated rollover protection system in regard to the roll bar, which is rounded into a U-shape at least in the top piece, so that it meets the above-mentioned requirements. 
   The solution of this problem occurs in a rollover protection system for motor vehicles with a roll bar, whose top piece is tubular and rounded into a U-shape, in that at least the tubular top piece consists of at least two axially separated, partially tubular shells of sheet metal, joined to each other and having different geometrical shape according to a nominal contour. 
   Thanks to the invented construction of tubular and U-shaped roll bars or correspondingly configured top pieces of roll bodies using partly tubular shells of sheet metal, it is possible to shape each individual shell individually with respect to the aforementioned requirements, using familiar hot and cold forming techniques. 
   A compound construction of the components of a rollover protection system is familiar in itself. 
   Thus, DE 100 13 376 C1 indicates a rollover protection system with a U-shaped roll bar, which can deploy and retract in a case firmly arranged on the vehicle, wherein the case is assembled from two sheet metal shells, each having two half shells to accommodate support tubes for the legs of the roll bar. In this case, the U-shaped roll bar is radially divided in the middle, in order to provide for an equalizing of tolerances when assembling and installing the roll bar. Therefore, this document gives no suggestion in the direction of the invention. 
   DE 203 03 691 U1 indicates a rollover protection device with a box like roll bar, which can deploy and retract in a case firmly arranged on the vehicle, wherein the roll bar is configured as a single or multiple-shell molded piece of fiber composite. In a two-shell layout, for example, two rectangular shells are fastened one on top of the other to form a profiled body. This shell construction has the sole purpose of increasing the stiffness and, thus, the resistance to buckling of the roll bar, and not to configure the shells individually in their outer contour in accordance with the required shape, course, and cross section of a roll bar. 
   The same also holds for the object of the earlier, not previously published patent DE 103 49 693 B3, whereby the shells of the rectangular box like roll bar, placed one on top of the other, can consist not only of fiber composite, but also of light metal or steel sheet. 
   DE 298 07 322 U1 indicates a shell-construction roll bar with a flat U-shaped configuration in its basic outline. In the basic configuration, the roll bar consists of a very wide, two-dimensional, rounded shell of fiber composite, or of sheet metal or other two-dimensional composite material, in which molded features are incorporated to give the shell the necessary strength. In one special configuration, a second two-dimensional shell is provided, overlapping the curvature of the first base shell and being welded to the base shell at the edge. This likewise has molded features to increase the strength of the roll bar. 
   This document gives no suggestion for a configuration of a tubular roll bar from partially tubular shells, whose individual deformability enables a different configuration satisfying the above-mentioned requirements. 
   Configurations and modifications of the invention are characterized in subsidiary claims and also appear from the description of the figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention shall be explained more closely by means of sample embodiments represented in various views in the drawings. 
     These show: 
       FIG. 1  in an isometrical view, a first embodiment of a two-shell, U-shaped roll bar with base piece, whose top piece shells are each formed onto the corresponding shells of the bottom piece as a single unit, 
       FIG. 2  an exploded view of the roll bar of  FIG. 1  to illustrate its shell construction, 
       FIG. 3  a longitudinal cross section of the roll bar, corresponding to the drawing in  FIG. 2 , 
       FIG. 4  a front view of the roll bar of  FIG. 1 , 
       FIG. 5  a side view of the roll bar of  FIG. 1  in cross section with foam padding and reinforcement or rubber/metal elements according to one version, 
       FIG. 6  a magnified cutout per  FIG. 1  with regard to the sectional area in the top piece, 
       FIG. 7  in an isometrical view, a second embodiment of a two-shell, U-shaped roll bar with corresponding two-shell bottom piece, being rigidly fastened in the bottom piece (e.g., by welding), and whose three-dimensional contour exhibits an irregular cross section and special shapes, 
       FIG. 8  a front view of the roll bar of  FIG. 7 , 
       FIG. 9  a side view of a two-shell roll bar with foam padding and a partial section of the bottom piece, in which an elastically deformable absorber element is installed in another embodiment, 
       FIG. 10  a side view with partial section of a two-shell, U-shaped top piece, which according to another embodiment is fastened to a deployable base body, 
       FIG. 11  the top piece of  FIG. 10  in front view, with bracket-like fastening shells formed onto it as a single piece (elongated top piece). 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The drawings show in schematized representations a rollover protection system for motor vehicles with a tubular and U-shaped roll bar or top piece  1 , which is assembled from two axially divided tubular shells  1   a  and  1   b . These shells consist of a sheet metal material, being individually shaped to the nominal contour required by the vehicle manufacturer using familiar cold and hot forming techniques. Thanks to the shell construction of the roll bar or its top piece, i.e., the fact that the shells can be individually deformed before being put together, it is relatively easy and economical to create a three-dimensional trend of the bar contour with irregular cross section, i.e., individual shapes of the roll bar geometry. 
   The shells are firmly joined together by familiar techniques, e.g., by welding, gluing, riveting, clinching (double bending), soldering, or by a combination of these techniques. They can be surface coated in familiar fashion, and also padded with an appropriate plastic foam. 
   Thanks to the steps of the invention, a modular construction of the bar or top piece is finally possible, i.e., the shells are nested together so that the width, the depth and the height of the bar or the top piece can be individually adapted to the vehicle conditions. 
   The bar or top piece  1  in the sample embodiment depicted in  FIG. 1  is joined as a single piece by a respective broad transitional segment  1   c  to a base piece  2 , which in turn serves to connect the bar to the body of the vehicle as a so-called rigid roll bar. This base piece is removably connected to the vehicle structure by the indicated fastening openings  2   c , e.g., to the rear wall in the floor of a convertible. In the systems according to the prior art, on the other hand, the rigidly installed roll bars are provided with costly add-on parts needing to be installed. 
   For an especially flexible configuration, according to one modification of the invention, and shown in particular by  FIG. 2  as well, the base piece  2  similar to the roll bar or its top piece likewise consists of molded shells  2   a ,  2   b  of sheet metal, which are joined together in the plane of the bar, and the respective shells  2   a  and  2   b  of the base piece are formed onto the corresponding shells  1   a  and  1   b  of the roll bar or its top piece as a single element, i.e., they are deformed together with the top piece shells from a common sheet metal piece. 
   As  FIG. 5  shows, spacers  3  are advisedly arranged inside the shells  2   a ,  2   b  of the base piece in the region of the fastening holes  2   c , which prevent the shells  2   a ,  2   b  from being forced together under a load. Additional reinforcement parts such as struts can also be placed inside the shells or in the region of the transition from the legs of the bar to the base piece. 
   The sectional surface in the top piece of  FIG. 5 , in conjunction with the corresponding cutout enlargement of  FIG. 6 , shows a typical, yet merely exemplified, desirable geometrical difference between the two shells  1   a ,  1   b , at top, with a foam padded part  4 , namely, a flattened front shell  1   a , facing the head of the passengers, and a rear shell  1   b , with a parabolic cross section. The flattened shell makes it possible to provide a thicker foam padding in the front region, which reduces the severity of injury in a crash. The flattening can be partial or over the entire surface. 
     FIGS. 7 and 8  show another embodiment of the invention, in which, unlike the embodiment of  FIG. 1 , the bar shells  1   a ,  1   b  are formed separately from the base shells  2   a ,  2   b  and are joined to each other. The assembled roll bar  1  is then inserted into corresponding openings in the assembled bottom piece and secured therein, e.g., by welding, as is symbolically indicated by a weld  5  in  FIGS. 7 ,  8 . 
     FIG. 9  shows, in another embodiment, a two-shell roll bar provided with foam padding  4 , whose legs are introduced in conventional manner into the bottom piece  2  and secured there, while advisedly an elastically deformable absorber element  6  in the form of a rubber/metal connection is provided in the “transitional region” according to EP 0 788 932 B1, so that the roll bar can yield somewhat at the base when subjected to loading. As an alternative, the transitional region can also be configured per EP 0 904 991 B1. 
   Also conceivable, per  FIG. 5 , are rubber/metal elements which brace the shells against each other and which at the same time have boreholes for screwing to the car body. In the sample embodiment shown, there is a two-shell construction for the roll bar and the mounting part, i.e., the base piece. In theory, one can also have more than two shells. 
   Given a rollover protection system, with a roll bar configured as a whole in the shape of a U-shaped roll bar with top piece and two parallel legs, it is advisable to configure this so that not only the top piece, but also the legs consist of shells of sheet metal that are joined together, each of them being formed as a single piece onto the corresponding shells of the top piece. Versions with round and rectangular tubes in lengths of 100 to 500 mm are conceivable. 
   Instead of a firm, i.e., rigid installation of the roll bar, according to  FIGS. 10 and 11 , one can also have a design such that the roll bar is controlled by sensor to deploy and is held in a case firmly mounted on the body, wherein advisedly the shell-construction U-shaped top piece  1  is fastened to a deployable base body  7  with its fastening shells  1   d , having fastening openings  1   e . In one variant, the fastening shells  1   d  can also be connected to a base piece. 
   Therefore, the invention is not confined to firmly installed roll bars, nor to U-shaped roll bars as a whole.