Abstract:
A roll over protection system for a passenger car, including at least one extended top unit ( 1 ) having substantially vertical beam(s) or tube(s) terminated or bridged by a connecting member ( 7 ) at their top ends. Initially in a crash, the upper part of the top unit only deforms by being bent backwards, thus creating a skid-plate against the ground and at the same time the survival room is impaired only negligibly.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a new concept for Roll Over Protection Systems (ROPS) for passenger cars, in particular cabriolets. It is useful for “pop up” (extendable) systems, but the general principle of the system cart advantageously be used also for fixed (non-extendable) ROPS. 
     In particular, the present invention relates to an improved system, giving advantages both within the protective scope in the case of a roll over accident, as well as cost and other benefits such as space utilization, less dependency on manufacturing tolerances and an improved guiding system (in the case of having an extendable system). 
     Many of the advantages and improvements are associated with the upper parts of a ROPS system, i.e. the “bar” itself. This improved bar (top unit) can either be a part of a cassette module, in which case two modules go into every car, or two top units can be installed in a common unit, such as a transverse beam module just behind the seats of the car. It is also within the inventive scope to use the invention for a single, wide system, covering the width of the car. 
     2. Description of the Related Art 
     There are a great number of such protection systems suggested in the prior art. 
     DE 197 81 835 T1 discloses a system where a roll over bar is provided through the bending of a tube. This is a very efficient and safe design with few welds and joints, thereby making it less prone to disintegration when subjected to large plastic deformations as in the case of a severe roll over crash. 
     DE 197 81 828 T1 discloses a roll over protection system where the bar is made out of only one extrusion, and is associated with a simple process to fabricate it. The bar legs are interconnected by means of an interconnecting plate that is partly cut away. 
     DE 195 23 790 discloses a roll over protection system where the two bars legs are interconnected by means of a plate. The plate extends along the main part of the extension of the bar legs. 
     SUMMARY OF THE INVENTION 
     The present invention relates to improvements regarding the behaviour of the roll over bar when the car turns over, and the bar hits the ground while the car is still moving. 
     In the case of a roll over accident situation, the car hitting the ground upside down, with the ROP units in place to take the crash forces, the units may imbed into the ground if the soil is soft (see  FIG. 4   a ). In this situation, the units may, due to the forward motion and inertia of the car, be bent at their roots, where the bending moments are greatest. Prior art units having constant cross sections along their height will tend to be deformed where the bending moments are highest. When this happens, the protruding parts of the units may be bent somewhat backwards, and the protected room of the seated persons may be impaired. 
     It is understood that the term backwards here refers to the forward motion direction of the vehicle. It is furthermore understood, that in addition to the compounded said forward motion of the car together with the roll over motion, in an accident, the vehicle may also have a spin (rotation) around its vertical axis. This may take the effect of the car being upside down, sideways or backwards or in a position in-between, when hitting the ground. Again, the term backwards here refers to the initial forward motion direction of the vehicle. The same may happen also against solid ground, such as when hitting a curb. 
     It is understood that in a roll over accident, the vehicle may frequently rotate several times thus subjecting the ROP system to said strains successively, before it comes to a standstill. 
     It is an object of this invention to improve the behaviour of a ROP system when encountering soft soil or being otherwise hooked against the ground in a roll over accident. 
     In accordance with the present invention there is provided a top ROP unit which may be formed and fabricated out of one extrusion, or one sheet metal blank, including: 
     Main tube(s) (beams, bars) which is(are) tapered (reduced cross sections) at the top, making it possible to pre-determine an upper part, which will bend in the case of the unit embedding in soft soil or getting hooked against a solid object. 
     Alternatively, the tube(s) may have one or more areas (sections) where they are weakened, to achieve the same effect. It is understood that these reductions of strength and stiffness may be achieved through a variety of means such as indenting the cross section, providing weakening holes or manipulating the wall material locally to have less strength, for example through local heat-treatment. 
     When the tube is bent locally it will disengage the grip of the soil or object which holds it, and slide over it without getting further bent. This means that only a small part of the protected room will be lost in the case of hitting soft soil or a curb. 
     Provided that the system does not get hooked, it will not deform as said, but will remain upright like prior art systems under the same condition. In other words, they ROP system adapts to the particular need of the crash situation. 
     It is here however recognized, that the tubes may consist of separately fabricated tubes which are connected to each other by structural connection means. 
     To further increase the protected room, the parts of the system are so configured, that it is possible to extend them higher in the case of an accident, in the case that extendable units are used. 
     This is achieved through having a slim lower connection between the tubes of the top unit, together with an indented connection of limited height between the supporting walls of the cassette or transverse beam module taking up the crash forces from the top unit. 
     The lower connection can further be bent to provide an even slimmer connecting member. 
     The top unit may have several vertical tubes with a connecting member between them which increases the ski-like sliding surface of the tubes—against soft soil when the upper part of the top unit is bent. 
     It is understood that the bending of the tubes and connecting members may be a rather sharp bend, creating in effect a ramp at an angle against the gripping soil or objects. Conversely, and particularly against soft soil, the deformation action may be more of the nature of a gradual, rolling-up action, creating a beneficial rounded shape, like the tip of a ski. 
     For extendable systems, there is a guiding system that is independent of the walls of the main tubes, and these tubes can then be formed to have a tapering section. 
     Separating the guiding from the tubes as described above, furthermore makes the guiding action during the extension of the system less dependent on the tolerances of the tubes, which is beneficial both when it comes to the need for (costly) small tolerances, as well as securing a consistent action of extension. 
     The guiding system can be encapsulated, and may contain the crash extension spring(s), and may be injection molded in plastic. There may be two guide units, one inside or near each main tube, or a central guide unit only. 
     The main tubes may be of a square cross-section, possibly with inverted sidewalls. Other tube sections may be applied, such as circular or semi-circular, elliptical and of polygon type with a plurality of side surfaces, or any given combination of the cross-sections along the lengths of the tubes. 
     The top part of the main tubes may be peeled off during fabrication to enable a further tapering of the strength of the main tubes. 
     The remaining connecting plate (web) may be rolled to a tube or semi-tube, to produce an agreeable initial crash surface, at the same time as stiffening the connection between the main tubes. 
     The formed parts of the top unit, together with added parts such as an arresting toothed crash rack, may be secured by welding. 
     In accordance with the present invention it is possible to improve crash protection. 
     The improved protection level in the case of the car overturning and hitting soft ground, a curb or a curb-like object, will particularly together with a higher system, provide improved protection for the occupants of the vehicle. 
     This comes in addition to the reduced cost of such a system compared to the current ones, possibly enabling a more widespread use of such systems in passenger cars. 
     These and further advantages can be achieved in accordance with the present invention as defined in the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, the invention shall be further described by examples and figures where: 
         FIG. 1  is a perspective view of one embodiment of an extendable top unit; 
         FIG. 2  is a perspective view of a second embodiment of an extendable top unit; 
         FIG. 3  is a perspective view of a third embodiment of an extendable top unit; 
         FIGS. 4   a - d  show the top unit in a turn over situation, where the car moves in an upside down position; and 
         FIG. 5  shows a second embodiment of predefined deformation behaviour of the tube(s) of the top unit. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1 , reference numeral  1  represents an extendable top unit, and reference numeral  2  denotes a cassette housing that supports the top unit. The top unit includes one extruded element  3  which has two closed section tubes  4  that are integral with a connecting web  5 . The web has a cut-out  6  which is higher than half of the height of the top unit. The web is rolled to form a semi-closed transverse section, called connecting member  7 , which may be welded to the end surfaces  8  of the main tubes (welds not shown). It is understood that the flat side of the top unit is normally facing the forward direction of the vehicle. The lower transverse connecting web  9  may be bent to provide an L or U-shaped connection  10  between the tubes. A toothed rack  11  is fixed to a remaining edge  12  of the web and one main tube by welding. 
     The main tubes  4  may have inverted sidewalls  13 , possibly at pre-determined parts of their extension (i.e. length) only. The cross-sections of the main tubes are manipulated to vary the strength of the tubes along their height. The end surfaces  8  of the tubes may be cut at an angle to continue the same effect upwards. The cassette  2  has an integral bottom plate  14 , and attachment flanges  15  more or less extending the height of the cassette. A reinforcement profile  16  bridges the top parts of the flanges together, in combination with anchoring the locking finger  17  (details not shown). 
     Crash extension springs (not shown) are housed in the separate guiding tubes  18  and  19 , which then not only guide the springs, but also the movement of the top unit in relation to the cassette. 
     The top tube  18  may be flanged to walls of the main tube, and secured, for example, by self-tapping screws (not shown). 
       FIG. 2  shows a second embodiment of the invention, where the bottom of the cassette has been eliminated, and where a lower guiding tube  20  is secured to the reinforcement member  22  by screws or rivets. A top guiding tube  23  now acts directly upon the rolled-up portion  7 , or is fixed to the top unit in some other fashion. Here the one centrally placed guiding unit may replace the previously used two units. The section “A-A” in  FIG. 2  shows how the reinforcement section is bolted directly to an indentation  26  of the cassette. One bolt may provide the pivot for the arresting finger  11  and a concentric release arm  25 . 
     It should be understood, that the edge  6  of the remaining web  5  will go between the reinforcement  22  and the cassette rear wall  27  where this wall is not indented. 
     It should be further understood that with this design, provided that a strong car structure allows it, the cassette  2  may be configured to be shorter (lower) than that of the prior art solutions. 
       FIG. 3  shows a third embodiment of the top unit  1  where it has been adapted to a substantial cross beam  28  with apertures  29 , to provide a ROP module (here a portion of one side shown only). Strength calculations have indicated, that such oblong apertures may not weaken the cross beam unduly as long as there are interconnecting bolts bridging the fore and aft sides of the beam. Here, the bolts  30  are again providing the pivots for the arresting finger as shown in  FIG. 2  (here not shown), together with interconnecting the sides of the beam. 
     The reinforcement  22  is inside the beam, and will be mounted together with the top unit and the guiding tubes  20  and  23  all pre-assembled as one unit. 
       FIG. 4   a  shows a passenger car, protected by ROPS, in an overturning situation. The car has a forward motion compounded by the rolling action, and the edge of the windscreen is touching the ground together with one side of the ROPS. 
       FIG. 4   b  shows an enlarged view of the initial contact between one ROP top unit and the ground, where the top unit is starting to embed (dig into) the relatively soft ground. 
       FIG. 4   c  shows the initial deformation of the top units following the force from the ground upon the system in the longitudinal direction of the car. The more the top of the main tubes are bent, the more the web between them will act as a skid-plate, lifting the car out of the grip of the soil. It is clear, that the more the top part is bent backwards, the more the weight and inertia-induced force from the car will support the local transformation bending of the main tubes. 
     Finally, in  FIG. 4   d  a steady state situation has settled where the local deformation has created a skid-plate at a sufficient size and angle to enable the top of the units to slide on the ground with a reduced force, thus stopping any further deformation of the system. 
       FIGS. 4   a - d  show the action of the new system in a car that is moving forward during contact with the ground. It should be understood, that in the case of the car having spun 180 degrees around a vertical axis in addition to the overturning movement, the car will hit the ground with the rear end forwards in the direction of motion. 
     It is furthermore understood, that a similar beneficial deformation of the top unit will occur in this situation. 
       FIG. 5  discloses a part of a top unit  40  where the tubes  41 ,  42  are connected/terminated by a connecting or bridging member  45 . The tubes may have one or more areas (sections)  43 ,  44  where they are weakened to achieve a predetermined deformation behaviour. The weakening of the tube(s) is done by indenting or compressing the cross section of the tube(s). It is understood that the tube(s) may have several weakened areas in succession along its (their) length, but differently weakened, to cater for eventual successive “hooking” impacts to the ROP system. 
     It should be understood that the locally arranged reductions of strength and stiffness in the tube(s) may be achieved through a variety of means. Other ways of achieving a predetermined deformation behaviour is to provide the tube(s) with weakening holes or manipulating the wall material locally to have less strength, for example through local heat-treatment. 
     In the examples there are shown various embodiments of the top unit. It should be understood that the principles of the invention can be exploited in other designs of a top unit as well, for instance top units using a conventional U-shaped bar, made out of one piece or plural pieces, and where its legs have weakened areas.