Abstract:
A rollover protection device includes a cassette housing which guides an extendable rollover bar. The cassette housing includes guidances for the rollover bar. The rollover bar is a single shell or multi-shell form part made of fibre reinforced plastic and has shell edge regions which at least partially extend parallel to the extension direction. The cassette housing is a hollow profile made from high strength material and is closed around the rollover bar and the guidance. The guidance is a plastic form part engaging at a shell edge region, is secured within the hollow profile and protrudes from the hollow profile at least downwards.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a filing under 35 U.S.C. § 371 of PCT/EP04/01231 filed Feb. 10, 2004, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     The invention relates generally to passenger protection devices for vehicles, and more specifically to a rollover protection device. 
     DE 43 42 400 A1 discloses one type of rollover protection device including a cassette housing made from aluminum and having side walls which are interconnected via a guiding body formed as an aluminum form part. The cassette housing has a bottom plate which grips around the lower ends of the rollover bar which is formed as a U-shaped tube bracket. The side walls as well are interconnected by a rear wall made from aluminum. The guiding body guides the U-legs of the rollover bar via slide bushings made from plastics. The U-legs of the rollover bar additionally are guided on plastic standpipes extending upwardly from the bottom plate. As a consequence, the cassette housing includes a compound structure of aluminum and plastic. Since the rear wall interconnects the side walls exclusively in the lower part of the cassette housing while the guiding body extends exclusively in the upper part of the cassette housing and between the side walls, the guiding body has to serve as a main load carrying element. The achievable crash performance in this type of device is correlated to the weight of the entire structural unit. 
     U-shaped cassette housings for receiving U-shaped tubular rollover bars are disclosed in, for example, U.S. Pat. No. 5,626,361 A (DE 43 14 538 A), EP 1 084 914 A, EP 1 038 735 A, and EP 1 028 050 A. These cassette housings are open at one broader side. Relatively small force transmitting areas are formed between the cassette housing having the U-cross-section and one open side and the vehicle body which force transmitting areas will be loaded by locally concentrated stress in a crash case. 
     A shell construction of rollover bars made from fibre reinforced compound plastic-is disclosed in, for example, DE 20 10 30 01 U. These rollover bars are directly guided between a profiled bulkhead of the vehicle body and a lateral beam made of fibre reinforced compound plastic material. 
     It would be desirable to provide a rollover protection device having a fair cost structure, extremely low weight and nevertheless an excellent crash performance. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In an exemplary embodiment, a vehicle rollover protection device is provided. The device comprises a cassette housing for guiding an extendable rollover bar. The cassette housing included guidances for the rollover bar, and the rollover bar is selectively positionable in a retracted position and an extended position. The rollover bar is a form part made of fibre reinforced compound plastic material in a structure comprising a single shell or several shells, and the rollover bar includes shell edge regions which at least partially extend parallel to a direction of extension of the rollover bar. The cassette housing is a hollow profile made from high strength material and having an upper profile end, a lower profile end, and narrow sides. The profile is open at both of the upper and lower profile ends and is closed around the rollover bar and the guidances. The rollover bar when retracted from the extended position into the hollow profile protrudes from the hollow profile at the upper and lower profile ends. The guidances are plastic form parts which engage at the shell edge regions and are firmly attached inside in the narrow sides of the hollow profile, The guidances protrude at least downwards beyond the lower profile end of the hollow profile. 
     Due to this mixed construction, the hollow profile made from a high strength material and the plastic form parts for guiding the rollover bar made of fibre reinforced compound plastic material can be pre-assembled for fair costs. Components (e.g., drive means and sensors, locking means and the like) needed for the function of the rollover protection device can be incorporated in the rollover protection device already during the pre-assembly process. High forces can be taken up via large areas and can be transmitted via large areas to a vehicle body, since the stable hollow profile surrounds on all sides the plastic material form parts which contribute during the force transmission in case of a crash, and the rollover bar. The construction results not only in a superior crash performance but also in a low weight of the compact rollover protection device. 
     The hollow profile expediently includes steel sheet material, in particular high strength steel sheet material. Due to the nature of the material and the hollow profile which is relatively short in relation to the length of the rollover bar, weight is saved significantly. High forces can be taken up and transmitted without problems in several different directions. 
     Alternatively the hollow profile even may consist of aluminum or magnesium or of high strength alloys of light metals, respectively. 
     A further alternative which is expedient with a view to saving weight refers to a hollow profile formed of fibre reinforced compound plastic material containing endless fibres in a matrix of plastic. 
     For manufacturing reasons and assembly reasons it may be expedient to combine the hollow profile of matching profiles or walls. The components can be interconnected by screwing, welding or other connection techniques. Such connections can withstand high forces without problems and even are able to dissipate energy in case of extremely high forces and may yield at least somewhat. A unitary hollow profile made from steel sheet material e.g. is formed by rolling from a section of a tube or a profile. 
     In some cases the incorporated plastic form parts do not only have the task of guiding the rollover bar and introducing the forces into the hollow profile, but the plastic form parts even can take up forces at their protruding length region even outside of the hollow profile and even can transmit such forces in some cases into the vehicle body. For this reason the plastic form parts should be injection moulded parts which are reinforced by short staple fibres or by longer fibres. Such injection moulded parts can be manufactured for fair cost. As an alternative, plastic pressing parts could be used which are reinforced by endless fibres. The moulding process of such pressing parts allows a great variety of shapes. In such cases thermoplastic or duroplastic plastic materials could be used. Glass e.g. can be used as the fibre material and may also be used in the fibre reinforced compound plastic material of the rollover bar and/or of the cassette profile section, e.g. in the form of prepregs which are available on the market and which are pre-impregnated by plastic material. 
     In order to allow to the transmission of forces into the vehicle bottom, the free ends of the plastic form parts should be formed with vehicle bottom connection means, either such that the plastic form parts are supported in pressing direction on the vehicle body or even are connected with the vehicle body by a form fit or a force fit, respectively. 
     In an expedient embodiment, the free ends of the plastic form parts may be interconnected by a lateral strut which may, in some cases, be provided with vehicle bottom connection means. 
     The lateral strut which also serves for stabilizing purposes may fulfill a secondary function such that it contains components for the actuation of the rollover bar like the actuator and a driving spring or a locking structure for the retracted rollover bar. Within a U-shaped body the lateral strut may be integrally connected with the form parts. Alternatively, the lateral strut can be manufactured separately (from the same or another material, e.g. light metal) and can be inserted later (by screwing, gluing, latching or the like). 
     In order to transmit occurring forces in the case of a crash via areas which are as large as possible and in a reliable fashion, a form fit ought to be provided between the plastic parts and the hollow profile, preferably by means of screws or bolts which as well penetrate the hollow profile. The screws or bolts can be inserted into force distributing sleeves within the respective plastic form part or could be inserted into at least one block which is formed in the plastic form part. The block may fit into a suitably formed cut-out of the hollow profile. The form fit also facilitates the pre-assembly of the rollover protection device. 
     A pawl supporting bolt may be held in at least one plastic form part. The pawl supporting bolt carries a pawl which supports and locks the extended rollover bar and further transmits the force acting on the pawl. Preferably, the pawl supporting bolt also penetrates the hollow profile. 
     In order to dissipate energy in case of a crash between the rollover bar and the vehicle body, a predetermined deformation region could be provided in the plastic form part and/or in the hollow profile. The predetermined deformation area is deformed by the pawl supporting bolt for dissipating energy during the transmission of forces. Such a predetermined deformation area e.g. could be an intentionally formed material weakening in the plastic form part and/or deformable or breakable through openings in the hollow profile which allow a predetermined dislocating movement of the pawl supporting bolt under load. 
     In order to assure that in case of a crash the rollover bar contacts the ground as early as possible and also with favourable lever arms in relation to the fixation location of the hollow profile in the vehicle body, the rollover bar may have a head structure which is thickened on all sides, in some cases even with broadened shoulders in the upper end region. This prevents a too easy intrusion of the rollover bar into soft ground. Furthermore, a desired abrasion property can be pre-set in this case for the ground contacting portions of the rollover bar. 
     At least one anchor within the rollover bar may be provided to define the extended end position of the rollover bar. The anchor even may grip around the edges on both sides of the hollow profile in order to prevent an undesirable expansion of the hollow profile due to reaction forces. 
     Furthermore, at least one local energy absorbing area could be provided in the rollover bar in order to intentionally abolish energy. 
     Further energy abolishment can be achieved by at least one cover on the hollow profile which cover digs into the edge region of the rollover bar during the unavoidable setting movement of the rollover bar during a rollover crash. The cover should, preferably, have a cutting edge which either removes material of the rollover bar or deforms under load. This effect can be enhanced by a mating nick in the edge region of the rollover bar. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary pre-assembled rollover protection device with an extended rollover bar. 
         FIG. 2  is a perspective view of the devise shown in  FIG. 1  without the rollover bar. 
         FIG. 3  is a perspective end view without rollover bar guidances. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the Figures, a rollover protection device  100  can be installed as a structural unit  102  into a vehicle body (not shown). In different embodiments, the structural unit  102  either is mounted in a shaft between lateral bulkheads of the vehicle body or directly at a vehicle body lateral bulkhead or at a lateral beam. The rollover protection device  100  has the task of protecting passengers in case of a rollover accident of the vehicle and is, for this reason, mainly used for convertibles. 
     The rollover protection device  100  is installed behind a seat rest (not shown), and, in particular, either behind each front seat or behind each rear seat. 
     Main components of the rollover protective device  100  include a cassette housing  104  and guidances  106  for the rollover bar  108 . The rollover bar  108  is displaceably guided by the cassette housing  104  between a retracted position and the extended rollover position shown in  FIG. 1 . A lock  110  is integrated into the cassette housing  104  for locking the rollover bar  108  in the rollover position. Anchors  112  mounted in the rollover bar  108  serve to limit the extension of the rollover bar  108  in the rollover position. Furthermore, an extension drive  114  is provided, e.g. at least one preloaded compression spring, which can be activated by an actuator  116  a soon as an integrated sensor (not shown) releases a latch which defines the retracted position. 
     In an exemplary embodiment, the rollover bar  108  is formed in shell construction of fibre reinforced compound plastic material. The rollover bar  108  may include a single shell or a plurality of shells, e.g. as shown, two shells. That is, the rollover bar  108  has a shell body  118  which in this case consists of two shells  120 ,  122  which are attached to each other by fixation elements  124 . The rollover bar  108  has substantially linear edge regions  126  at which the guidances  106  engage. The rollover bar  108  may comprise a thickened head structure  128  and/or shoulders  130  protruding outwardly beyond the edge regions  126  in order to positively influence the abrasion property and/or the ground digging property of the rollover bar  108  in case of a crash. 
     The cassette housing  104  includes a hollow profile  134  which is open at both ends and which surrounds the rollover bar  108  and the guidances  106  on all sides. The hollow profile  134  consists of an e.g. high strength material in one embodiment. In the case shown the hollow profile  134  consists of high strength steel sheet material, and e.g. is made from two profiles  134 ,  136  which are connected in the region of the edge flanges  140 . The connections may include welding, screwing, clinching, riveting or the like. The hollow profile  134  even could be one piece and could be formed by e.g. rolling. 
     The hollow profile  134 , alternatively, could consist of aluminum or magnesium or of high strength alloys of such light metals. As a further alternative, the hollow profile could be made of a fibre reinforced compound plastic material which may be similar or different from the fibre reinforced compound plastic material of in the rollover bar. The height dimension of the hollow profile  134  in the shown embodiment is smaller than the width dimension. The guidances  106  at least are attached with a form fit in the narrow side areas of the hollow profile  134 . 
     Each of the guidances  106  is a plastic material form-part  142  of longitudinal format and has an inner guiding track  144  for one rollover bar edge region  126 . The plastic form part  142 , furthermore, includes reinforced upper fixation regions  146  and, in some cases, reinforced lower fixation regions  148  including vehicle body bottom connection means  150 . In some cases the free ends of the form parts  142  may be interconnected by at least one lateral strut  152 . The actuator  116  and/or the vehicle body bottom connection means  150  may be arranged at the lateral strut  152 . In case that exclusively the hollow profile  134  is used for transmitting forces into the vehicle body, the guidances  106  could be designed shorter then shown (indicated in dotted lines). Both form parts  142  and the lateral strut  152  could form a one-piece U-shaped structural unit. Alternatively, the lateral strut  152  may be a separate form part, e.g. made form light metal or plastic into which sockets e.g. for the actuator  114  and/or the extension spring are formed. This form part easily can be e.g. latched into openings of the form parts including the guidances  106 . 
     The forms parts  142  may be injection moulded parts made from plastic material which is reinforced with short staple fibres or long fibres, or could be pressing form parts made of fibre reinforced compound plastic material, respectively. 
     In order to secure each form part  142  with a form fit in the hollow profile  134  e.g. fixation screws or bolts  154  could be provided which penetrate through the hollow profile  134 . The fixation screws or bolts  154  e.g. may be equipped with sleeves  156  for distributing forces and/or spacing purposes. The hollow profile  134  has fixation bores. Alternatively and additively, the form part  142  may have an integrated block  158  which is fitted into a cut-out  160  formed in the hollow profile  134 . 
     The lock or locking device  110  may include, preferably at one side of the rollover bar, a pawl  162  which is carried by a pawl supporting bolt  164 . The pawl co-acts with a latching cogging  165  indicated in  FIG. 3  (e.g. consisting of light metal) in the edge region  126 . The pawl supporting bolt  164  may penetrate through supporting openings  166  in the hollow profile  134 . Expediently, predetermined deformation areas  168  are provided in the form part  142  and/or in the hollow profile  134 . The predetermined deformation areas  168  yield in predetermined fashion under the load on the extended rollover bar  108  in order to dissipate or abolish energy. The predetermined deformation areas  168  may include weakened regions in the form part  142  and/or weakened regions in the hollow profile  134 , e.g. keyhole like formed supporting openings as indicated in dotted lines with reference numeral  168 . 
     The spring constituting the extension drive  114  may be guided in a tube  170  provided in the interior of the rollover bar  108 . The spring may be supported at the vehicle body bottom and/or the lateral strut  152 , respectively. 
     The anchors  112  limiting the extended rollover position e.g. consist of aluminum and are inserted into one open end of the rollover bar  108 . Each anchor  112  is connected at  172  ( FIG. 3 ) with the rollover bar  108 . Each anchor  112  (there might be provided a single anchor only) has an edge-shaped insertion part  174  which fits into the inner cross-section of the rollover bar  108  and two outwardly extending hooks  176  which will be caught at the lower edge regions of the section of the hollow profile  134 , e.g. in indentations  177  formed at each side. The hooks  176  grip around the edge regions in order to prevent an expansion of the hollow profile  134  in case of occurring reaction forces. 
     The fibre reinforced compound plastic material of which the rollover bar  108  and/or the form part  142  may consist, preferably contains endless fibres of glass in a matrix of plastic material, e.g. of a thermoplast. These components are processed in a hot pressing process to the desired shape. The endless fibres expediently are contained in prepregs which are available on the market and which are already pre-impregnated with the plastic material. The prepregs are e.g. available as fabrics or fleeces. Other high strength fibres, e.g. carbon fibres, in some case cases may be used alternatively or additively. 
     The plastic form parts  142  are firmly locked to the stable hollow profile  134  in the rollover protection device  100  in order to introduce the high forces from the rollover bar  108  into the hollow profile  134  in case of a rollover accident. The hollow profile  134  then transfers the forces into the vehicle body. The plastic form parts  142  may contribute to the load transfer due to the design and in some cases via a support at the vehicle body, in particular at a support at the vehicle body bottom, and also may transfer forces, i.e. will behave like a kind of a bendable beam and/or of a compression pillar in order to also transfer forces. 
     The hollow profile  134  can be formed of profiles or from a U-profile and an essentially planar covering plate. In some cases the hollow profile  134  even can be a unitary structure. 
     In a simple embodiment the hollow profile  134  defines a rectangular box in the shown embodiment. The narrow side regions of the hollow profile  134  are drawn in relative to the middle section of the hollow profile along the entire height and in the regions in which the plastic form parts  142  are attached by form fit such that the inner width is larger in the middle region than in the narrow side regions. 
     The rollover protection device  100  includes the structural unit  102  which can be pre-assembled and pre-tested. The structural unit  102  is of compact size, is very light and has a superior rollover crash performance. The crash performance assures that all loads occurring in case of a crash are reliably introduced in many different directions into the vehicle body. The broadened shoulders  130  or the head structure  128  of the rollover bar  108  come into contact with the ground very early. Furthermore, the broadened region in the upper end region of the rollover bar (the head structure  128 ) prevents that the rollover bar digs too easily into soft ground. In this regions, in some cases, a wear resistant zone can be formed by an increased mass concentration and/or with the help of wear inserts. These measures as well contribute to the good crash performance. 
     As any energy dissipation already between the rollover bar  108  and the vehicle body means a positive contribution to the crash performance in the case of a rollover accident, even further measures for dissipating energy may be expedient. 
     In  FIGS. 1 ,  2  a nick  180  is indicated in dotted lines in one edge region  126  of the rollover bar  108 . In the extended position of the rollover bar  108  the nick  180  is located close to a sharp edge of a cover  182  which is provided sidewardly at the hollow profile  134 . In case of an introduced load, the rollover bar tends to set or tilt sidewardly in relation to the hollow profile  134 , in particular in a case in which at one side only a pawl support is provided. In this case the cover  182  will dig into the edge region  126  in order to peel off material during the unavoidable setting motion of the rollover bar  108  such that energy is dissipated. The nick  180  could even be dispensed with for this effect if the cover  182  has enough stability and/or has a very sharp edge. 
     A further measure to dissipate energy is provided by at least one locally provided energy absorption area  184  which responds in case of a crash such that energy is significantly dissipated. The energy absorption area  184  can easily be formed in the rollover bar  108  consisting of fibre reinforced compound plastic material, because this material allows an extremely large degree of freedom for shaping the rollover bar  108 . 
     The latter measure can be incorporated into the rollover bar  108  by a special design and/or a variation of the wall thickness and/or a variation of the fibre content and the like. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.