Abstract:
A roll bar assembly capable of punching through a rear window on deployment comprises a deployable u-shaped roll bar fitted with a pin made of hard material. The pin may be fixed to an upper surface of the roll bar or may be housed inside the top portion of the roll bar and deployed at the appropriate moment by pyrotechnic means.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to roll bar assemblies for vehicles and particularly for convertible motor vehicles having a rear window made of glass.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many convertible vehicles are provided with roll bars or hoops for protecting the driver and passengers in the event of the vehicle overturning. Some roll bars currently found on motor vehicles are fixed in position and some are stowed in a retracted position out of sight and deployed when required.  
         [0003]     GB-A-157543 discloses a deployable roll bar which pivots from a horizontal stowed position to a vertical deployed position. The roll bar is located behind the front seat of a vehicle and is triggered by means of a pyrotechnic device in conjunction with a sensor responsive to vehicle rotational acceleration or angle of rotation.  
         [0004]     U.S. Pat. No. 5,458,396 discloses a deployable u-shaped roll bar that is stowed in a retracted position in the headrest or backrest of a seat and which extends upwards above an occupant&#39;s head in a deployed position. The roll bar&#39;s deployment system includes a spring-loaded release member and a hold member so that on deployment, the roll bar may be forced upwards by the action of the spring and locked in an extended position by the hold member.  
         [0005]     GB-A-2,184,586 discloses sensor means for controlling deployment of a roll bar. A first sensor comprises an inertia switch located centrally in the vehicle and a second sensor means comprises switches located on the rear wheels of the vehicle, each switch being closed when the rear wheel suspension is completely extended, and a third sensor comprising a tilt switch. This combination of switches facilitates deployment of the roll bar when overturning of the vehicle is imminent and inhibits deployment when the vehicle is lifted in a workshop or is driven over a hump.  
         [0006]     When designing either fixed or deployable roll bar arrangements for motor vehicles, certain constraints have to be taken into account.  
         [0007]     Firstly packaging constraints must be considered, so that the roll bar can be located in the vehicle optimally.  
         [0008]     Additionally for protection, the static or deployed position has to be sufficiently high in order to offer a protective ‘zone’ in which the occupants are retained, thus avoiding or minimising contact between an occupant&#39;s head and the road surface when the vehicle is rolling or static on the ground.  
         [0009]     Further, there must be allowance for the operation of a roof-folding mechanism and the travel envelope when folding or unfolding the roof.  
         [0010]     Deployable roll bars must be able to reach a point where protection is afforded irrespective of the position of the roof, i.e. up or down.  
         [0011]     Known roll bar arrangements meet the above constraints by virtue of roof design. That is, the roof is positioned so that it clears the roll bar in its deployed condition, thus allowing the roll bar to function in either case of roof position, up or down. This has led to a compromise on the styling, aerodynamics and other factors related to the roof design, this being undesirable from a marketing and competitive point of view.  
         [0012]     Thus there is a need for a deployable roll bar which will operate within the constraints mentioned above and which will allow design freedom with regard to the overall appearance of the vehicle, particularly the roof-line, the size and location of the rear window and the possibility of utilising glass as the material for the rear window.  
       SUMMARY OF THE INVENTION  
       [0013]     In a first aspect, the present invention provides a roll bar assembly for a vehicle, said assembly including a deployable roll bar incorporating a device for breaking a rear window of the vehicle on deployment of the roll bar.  
         [0014]     In a second aspect, the present invention provides a seat for a vehicle, which in said seat is incorporated the roll bar assembly in accordance with said first aspect recited above.  
         [0015]     In a third aspect, the present invention provides a vehicle incorporating the roll bar assembly in accordance with said first aspect recited above.  
         [0016]     In a fourth aspect, the present invention provides a vehicle incorporating the seat in accordance with said second aspect recited above.  
         [0017]     In one embodiment, the device comprises a pin, in part fixed to and in part, protruding from an upper surface of the roll bar.  
         [0018]     The pin may be fixed to the upper surface of the roll bar by means of a threaded joint.  
         [0019]     A protruding part of the pin may have a conical, frusto-conical or domed shape. Such shapes have been found to break a glass window satisfactorily, causing it to shatter into small pieces. Preferably, the protruding part of the pin is made from a hard material having a hardness of at least 1000 Vickers, e.g. tungsten carbide.  
         [0020]     In an alternative embodiment, the roll bar is provided with an orifice in an upper surface thereof, and the device comprises a pyrotechnic actuator incorporating a deployable pin, said actuator being located within the roll bar such that on deployment of the actuator, the deployable pin extends through the orifice beyond the upper surface of the roll bar.  
         [0021]     This alternative embodiment is advantageous in that in the stowed, non-deployed position, no protrusion extends from the roll-bar. It also optimises styling freedom through the ability to locate the roof of the vehicle and trim features in lower positions. (The embodiment having fixed, protruding pins requires extra clearance space between the roll bar and vehicle trim). The alternative embodiment is also safer to handle during vehicle assembly and service.  
         [0022]     The pyrotechnic actuator may be fixed to the upper surface of roll bar by means of a threaded joint.  
         [0023]     An upper part of the deployable pin may be conical, frusto-conical or dome shaped.  
         [0024]     An upper part of the deployable pin may be composed of tungsten carbide, or any suitable material having a hardness of at least 1000 Vickers.  
         [0025]     In either embodiment, the roll bar assembly may further include spring-loaded means and a solenoid switch for effecting deployment of the roll bar. Alternatively, the spring-loaded means may be activated by pyrotechnic means rather than a solenoid switch. Alternatively to the spring-loading, the roll bar may be actuated pyrotechnically.  
         [0026]     The roll bar and breaking device may be included in the back rest of one or all of the seats of a vehicle and the roll bar may be an inverted u-shape. Alternatively, a roll bar and breaking device may be located behind one or all of the seats of the vehicle, or may be positioned behind the seats and extend across the vehicle from one side to the other. The roll bar may include just one breaking device preferably located close to an outboard shoulder of the ‘U’ or two devices, each located close to each shoulder of the ‘U’.  
         [0027]     The inclusion of two breaking devices ensures that, no matter whether the roll bar is fitted to either a left hand seat or a right hand seat, on deployment, the pin will hit the rear window before the roll bar does. If only one breaking device is incorporated, then depending on where it is located, its length has to be chosen so that on deployment, it makes contact with the rear window before any other part of the roll bar does. In either case where the roll bar and breaking device is fitted to a seat or behind a seat, the invention further provides an optional item of trim which is frangible and located so as to cover the roll bar when the roll bar is in a stowed position and to fracture on deployment of the roll bar.  
         [0028]     Alternatively the item of trim may be removable and displaced on deployment of the roll bar.  
         [0029]     Provision of such means for covering the roll bar and breaking means whilst in the stowed, non-deployed position not only benefits styling but also, in the case of the embodiment having a fixed protruding pin, it prevents items of clothing, luggage or passengers themselves from coming into contact with the pin. The item of trim may form a part of the seat assembly or part of the vehicle trim.  
         [0030]     The roll bar assembly may further include a sensor for detecting imminent rollover of the vehicle and for generating control signals for deployment of the roll bar and of the pyrotechnic actuator (if fitted.)  
         [0031]     A delay may be introduced between deployment of the roll bar and deployment of the actuator so that the roll bar can first puncture or displace and clear any covering trim provided before the pin is ejected through the orifice provided in the roll bar. This ensures that the pin will not catch on the trim as it moves upwards on deployment.  
         [0032]     Hence the present invention provides a means for allowing deployment of a roll bar through a vehicle roof, specifically the rear window glass, so that the desired deployed position of the roll bar can be reached irrespective of roof position.  
         [0033]     It has been discovered by the inventors that a conventional roll bar without the provision of a breaking device is incapable of fracturing a glass rear window on deployment, unless the energy of the deployment is increased to such a level whereby static loads on the roll bar assembly are unacceptably high and so the risk of injury in mis-use situations increases. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]     Some embodiments of the invention will now be described by way of example only with reference to the drawings, of which;  
         [0035]      FIG. 1  is a perspective view of a roll bar arrangement in accordance with a first embodiment,  
         [0036]      FIG. 2  is a cross-sectional view of the roll bar  FIG. 1   
         [0037]      FIGS. 3A and 3B  are schematic diagrams illustrating the incorporation of the embodiment of  FIG. 1  in a vehicle in a stowed position ( FIG. 3A ) and a deployed position ( FIG. 3B ),  
         [0038]      FIG. 4  is a schematic diagram illustrating the incorporation of the embodiment of  FIG. 1  in a vehicle seat,  
         [0039]      FIG. 5  is a perspective view of a roll bar arrangement in accordance with a second embodiment,  
         [0040]      FIG. 6  is a partially-sectional view of the roll bar of  FIG. 5 ,  
         [0041]      FIG. 7  is a plan view of a pyrotechnic actuator in a deployed configuration,  
         [0042]      FIGS. 8A and 8B  are schematic diagrams illustrating the incorporation of the embodiment of  FIG. 5  in a vehicle in a stowed position ( FIG. 8A ) and a deployed position ( FIG. 8B ) and  
         [0043]      FIG. 9  is a schematic diagram illustrating the incorporation of the embodiment of  FIG. 5  in a vehicle seat. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0044]     In  FIG. 1 a  hollow inverted u-shaped roll bar  1  co-operates with a roll bar release mechanism  2  (whose housing alone is shown in  FIG. 1  for the sake of clarity). In this example the release mechanism is a spring-loaded arrangement. (Alternatively, the spring-loaded arrangement could be replaced with a pyrotechnic mechanism). The release mechanism is activated by a release device  3  which in this example is a solenoid switch. (As an alternative, a pyrotechnic actuator could be used).  
         [0045]     The roll bar  1 , spring-loaded arrangement  2  and solenoid switch  3 , operate in a known manner, i.e. when a remotely-generated trigger signal is received by the solenoid switch  3 , the switch activates the release mechanism  2  and as a consequence, the roll bar  1  is deployed upwards out of the housing  2  (in the direction of arrow A). Conventional locking means (not shown) prevent the roll bar  1  from moving any further or from being pushed back into the housing by any external force once the roll bar  1  has reached its fully-deployed position.  
         [0046]     In accordance with the first embodiment, the roll bar  2  is fitted with two pins  4 .  
         [0047]     With reference to  FIG. 2 , each pin  4  consists of a threaded portion  5 , an integral lock nut  6  and an end portion  7  having a frusto-conical form. The threaded portion co-operates with a tapped hole  8  in the upper surface  9  of the roll bar. Each pin  4  is located close to the shoulders  10 ,  11  of the roll bar. The threaded portion  5  and lock nut  6  are made of steel and the end portion  7  is composed of tungsten carbide and bonded to the lock nut  6  using a suitable epoxy resin adhesive. (Alternatively, the end portion  7  can be brazed to the lock-nut  6 ).  
         [0048]     With reference now to  FIG. 3A  the roll bar arrangement of  FIGS. 1 and 2  is shown incorporated in a convertible vehicle  12  which includes a removable or folding roof  13  incorporating rear window  14  made of glass, a seat  15  and rear bulkhead  16 . The rest of the vehicle is omitted for the sake of clarity. The roll-bar arrangement  1 ,  2 ,  3 ,  4  of  FIGS. 1 and 2  is secured to the rear bulkhead  16  behind the seat  15 . Also fitted to the vehicle is a vehicle motion sensor  17 , of conventional design, whose electrical output (not shown) is connected to the solenoid switch  3 .  
         [0049]     An item of trim  18  is positioned over the upper surface of the roll bar, hiding the roll bar  1  from view whilst in its un-deployed, stowed position in the housing  2 .  
         [0050]     Operation of the embodiment of  FIG. 3A  will now be described with particular reference to  FIG. 3B .  
         [0051]     When the vehicle motion sensor  17  detects that rollover of the vehicle  12  is imminent, it transmits a trigger signal to the solenoid switch  3  which in turn, activates the release mechanism  2 . Consequently, the roll bar  1  is rapidly deployed upwards (in the direction of arrow B). As the roll bar  1  deploys in this way, it displaces the trim item  18  and continues upwards towards the glass rear window  14  whereupon the end portion  7  of at least one of the pins  4  strikes the window causing the latter to shatter into many fragments  19 . Once the roll bar  1  is deployed to its fullest extent, it locks in position just beyond the roof line as defined by the profile of the rear window  14  and clear of the head of any occupant of the seat  15 , thus affording the necessary protection.  
         [0052]     The alternative arrangement of  FIG. 4  shows the roll bar arrangement of  FIGS. 1 and 2  incorporated in the backrest of the seat  15  rather than being attached to the rear bulkhead. Also in this example, the trim item  18  is made of a frangible material. Otherwise, the constituents of the arrangement illustrated in  FIG. 4  are the same as those in  FIGS. 3A and 3B .  
         [0053]     On deployment of the arrangement of  FIG. 4 , as the roll bar  1  is deployed upwards, it first breaks through the frangible trim item  18  and then strikes and shatters the rear window  14 .  
         [0054]     A second embodiment will now be described with reference to  FIGS. 5, 6  and  7 .  
         [0055]     In  FIG. 5 a  hollow inverted u-shaped roll bar  20  co-operates with a roll bar release mechanism  21  (whose housing alone is shown in  FIG. 1  for the sake of clarity). In this example the release mechanism is a spring-loaded arrangement. (Alternatively, the spring-loaded arrangement could be replaced with a pyrotechnic mechanism). The release mechanism is activated by release device  22  which in this example is a solenoid switch. (As an alternative, a pyrotechnic actuator could be used).  
         [0056]     The roll bar  20 , spring loaded arrangement  21  and solenoid switch  22  operate in a known manner, i.e. when a remotely-generated trigger signal is received by the solenoid switch  22 , the switch activates the release mechanism  21  and as a consequence, the roll bar  20  is deployed upwards out of the housing  21  (in the direction of arrow A). Conventional locking means (not show) prevent the roll bar  20  from moving any further or from being pushed back into the housing by any external force once the roll bar  20  has reached its fully-deployed position. The delay between receiving a trigger signal at the solenoid switch  22  and deployment of the roll bar  20  is typically no more than 150 ms.  
         [0057]     In accordance with the second embodiment, the roll bar  20  is fitted with two pyrotechnic actuators  23  to be described hereinbelow.  
         [0058]     With particular reference to  FIG. 6 , each pyrotechnic actuator  23  is secured to an upper surface  24  of the roll bar  20  by means of a screw-threaded part  25  which co-operates with a tapped hole  26  in the upper surface  24 . Each actuator  23  is positioned so that its upper face is substantially flush with the upper surface  24  of the roll bar  20  and is put into position by feeding it through an access hole  27  provided in a lower surface  28  of the roll bar  20 . Electrical leads  29 , connecting each actuator  23  to a control circuit (to be described hereinbelow), are fed through the hollow part of the roll bar  20  into the housing  21 .  
         [0059]     Inside each pyrotechnic actuator  23  is a combustion chamber, stored pyrotechnic material in powder form and a deployable pin  30  having an end portion  31 , frusto-conical in form and made from tungsten carbide. A signal supplied via the electrical leads  29  activates an igniter inside the actuator. The time delay between ignition and deployment of the pin to its fullest extent is typically 2 ms.  
         [0060]      FIG. 7  shows a pyrotechnic actuator  23  in its deployed configuration with the pin  30  having been ejected from its stowed position.  
         [0061]     Each actuator  23  deploys its pin  30  in a conventional manner, and is locked into a fixed position once it has been deployed to its fullest extent.  
         [0062]     With reference now to  FIG. 8A  the roll bar arrangement of  FIGS. 5 and 6  is shown incorporated in a convertible vehicle  32  which includes a removable or folding roof  33  incorporating rear window  34  made of glass, a seat  35  and a rear bulkhead  36 . The rest of the vehicle is omitted for the sake of clarity. The roll bar arrangement  21 ,  22 ,  23 ,  24  of  FIGS. 5 and 6  is secured to the rear bulkhead  36  behind the seat  35 . Also fitted to the vehicle is a vehicle motion sensor  37 , of conventional design, whose electrical output (not shown) is connected to the solenoid switch  22 .  
         [0063]     A delay circuit  38  is also fitted to the vehicle. This circuit is electrically connected to the motion sensor  37  and to each pyrotechnic actuator  23 .  
         [0064]     An item of trim  39  is positioned over the upper surface of the roll bar, so hiding the roll bar  20  from view whilst in its undeployed, stowed position in the housing  21 .  
         [0065]     Operation of the embodiment of  FIG. 8A  will now be described with particular reference to  FIG. 8B .  
         [0066]     When the vehicle motion sensor  37  detects that rollover of the vehicle  32  is imminent it generates and transmits a trigger signal to the solenoid switch  22  and to the delay circuit  38 . Consequently, the solenoid switch  22  activates the release mechanism  21  and the roll bar  20  commences to move upwards in the direction of arrow B.  
         [0067]     As the roll bar  20  deploys in this way, it displaces the trim item  39  and continues upwards towards the glass rear window  34 . After a pre-determined time delay corresponding to the time elapsed between generation of the trigger signal by the motion sensor  37  and the roll bar  20  displacing the trim item  39 , the delay circuit relays the trigger signal to the pyrotechnic actuators  23  which fire their pins  30 . As the pins  30  reach their fully deployed position, the end portion  31  of at least one of the pins  30  strikes the window  34  causing the latter to shatter into many fragments  40 . Once the roll bar  20  is deployed to its fullest extent, it locks in position just beyond the roof line as defined by the profile of the rear window  34  and clear of the head of any occupant of the seat  35 , thus affording the necessary protection.  
         [0068]     The alternative arrangement of  FIG. 9  shows the roll bar arrangement of  FIGS. 5 and 6  incorporated in the backrest of the seat  35  rather than being attached to the rear bulkhead. Also in this example, the trim item  39  is made of frangible material. Otherwise, the constituents of the arrangement illustrated in  FIG. 9  are the same as those in  FIGS. 8A and 8B , and they operate in the same manner. On deployment of the arrangement of  FIG. 9 , as the roll bar  20  is deployed upwards, it first breaks through the frangible trim item  39 . Once this is cleared, the actuator pins  30  are deployed and the roll bar  20  continues upwards, whereupon the end portion  31  of at least one of the pins  30  strikes the window  34  causing it to shatter.