Abstract:
An impact energy transmitting arrangement ( 10 ) for transmitting energy, which arises during impact between a vehicle ( 12 ) on which the arrangement ( 10 ) is mounted and a foreign body, to a vehicle structure ( 14 ). The arrangement includes first means ( 18 ) displaceable in a first direction, and second means ( 20 ) adapted for co-operation with the first means. The first and second means are operable such that the arrangement, below a first predetermined value of a parameter representative of the energy to be transmitted, presents a first resistance-to-displacement value and, above the first predetermined value, presents a second resistance-to-displacement value. The first resistance-to-displacement value is greater than the second resistance-to-displacement value. In this manner, a bumper assembly which is stiff at very low speeds is rendered less stiff at higher speeds which otherwise could cause injury to pedestrians.

Description:
TECHNICAL FIELD 
     The present invention relates to an impact energy transmitting arrangement for transmitting energy, which arises during impact between a vehicle on which said arrangement is mounted and a foreign body, to the vehicle structure. The invention further relates to a method of transmitting energy, which arises during impact between a vehicle on which said arrangement is mounted and a foreign body, to the vehicle structure. 
     BACKGROUND OF THE INVENTION 
     Motor vehicle manufacturers are constantly striving to provide vehicles which, in the event of a collision, reduce the risk of injury to persons involved in the collision. These persons may be occupants of the vehicle or a pedestrian which is struck by the vehicle. To this end, vehicles are nowadays designed with so-called deformation zones which deform in a controlled manner to thereby absorb energy which arises during impact between the vehicle and an object. The amount of energy which arises in a collision is proportional to the square of the relative velocity between the vehicle and the object at impact. Obviously, the risk of injury to occupants of vehicles is increased at higher speeds. Due to the considerable amounts of energy which arise as a result of high speed collisions, the deformation zones must exhibit a certain degree of stiffness, or resistance to deformation, to function effectively at those high speeds. 
     Most collisions between vehicles and pedestrians occur in built-up areas in which the speed of the vehicles is relatively low. For example, most jurisdictions impose a speed limit in built-up areas of about 50 km/h. Due to the relatively light weight of most pedestrians, the amount of energy which arises in a low speed collision between a vehicle and a pedestrian is relatively low. This implies that the deformation zones of the vehicle are not caused to deform to any great extent and therefore a large amount of the energy is transmitted to the pedestrian, possibly resulting in injury. 
     In an attempt to reduce pedestrian injury, the prior art has suggested various ways of reducing the stiffness of a vehicle during collision with a pedestrian. For example, in U.S. Pat. No. 6,050,624 a bumper mounting structure is disclosed having a dual rate shock absorbing member which offers less resistance to deformation at low impact energy amounts and higher resistance to deformation at higher impact energy amounts. In the bumper arrangement according to DE-A-199 42 167, longitudinal displacement of a sliding member is restricted by a pin at higher speeds or if a sensor detects the proximity of an object larger than a pedestrian. At lower speeds, the pin is disengaged from the sliding member, thereby facilitating displacement of the sliding member to progressively absorb the impact energy. EP-A-0 983 909 describes a stiffener assembly for a bumper system of a motor vehicle, which assembly includes a stiffener operatively connected to the bumper system and movable between an up position and a down position based on the speed of the vehicle. 
     A disadvantage with components which are readily deformable at low impact speeds is that such components may need to be replaced as a result of a low speed collision in which the risk of personal injury is negligible. Such may be the case, for example, in a collision at parking speeds between a vehicle and, say, a lamppost. Furthermore, in order to keep production costs low, any impact absorbing or transmitting arrangement should be as simple as possible. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an impact energy transmitting arrangement which is simple in operation and which survives low speed impacts intact, but which nevertheless offers reduced risk of injury to pedestrians. 
     This object is achieved in accordance with the present invention by the impact energy transmitting arrangement as claimed in claim  1 . 
     It is a further object of the present invention to provide a method of reducing risk of pedestrian injury in a collision between a vehicle and a pedestrian. 
     This object is achieved in accordance with the present invention by the method as claimed in claim  29 . 
     The invention is based on the insight that a collision between a pedestrian and a vehicle at very low speeds is survivable for the pedestrian even if the vehicle were to be essentially rigid. This is because the amount of energy which arises during impact is relatively low. However, as speed increases, and as previously been mentioned, the amount of energy increases as a square of the speed. This necessitates the provision of a readily displaceable member which can be used to ensure that the energy is absorbed in such a manner that as little energy as possible is transmitted to the pedestrian. 
     Thus, in the present invention an impact energy transmitting arrangement is provided with first means displaceable in a first direction, and second means adapted for co-operation with the first means. The first and second means are operable such that, as a result of an impact between the vehicle and a foreign body for which the energy to be transmitted is below a first predetermined value, the arrangement is stiffer than it would be as a result of an impact for which the energy to be transmitted is above the first predetermined value. 
     In order that vehicle deformation zones shall function adequately during high speed collisions, an arrangement which is stiffer than that for optimal pedestrian injury reduction is required. In accordance with an preferred embodiment, the first and second means are operable such that, as a result of an impact between the vehicle and a foreign body for which the energy to be transmitted is above a second predetermined value, the arrangement is stiffer than it would be as a result of an impact at a velocity below the second predetermined value. The first and second predetermined values may correspond to velocities of about 15 km/h and 60 km/h, respectively, for typical collisions between a vehicle and a pedestrian. 
     Preferred embodiments of the arrangement according to the present invention are detailed in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in the following by way of example only and with reference to the embodiments illustrated in the drawings, in which: 
         FIG. 1  is a schematic perspective view of a first embodiment of an impact energy transmitting arrangement according to the present invention; 
         FIG. 2  is a sectional view along line II—II of  FIG. 1 ; 
         FIG. 3  is a schematic elevation view of a component of the arrangement of the first embodiment according to the present invention; 
         FIG. 4A  is a schematic sectional elevation view corresponding to  FIG. 2  with the arrangement in its non-influenced condition; 
         FIG. 4B  is a schematic sectional view corresponding to  FIG. 4A , though with the arrangement in a condition after a typical low speed impact; 
         FIG. 4C  is a schematic sectional view corresponding to  FIG. 4A , though with the arrangement in a condition after a typical impact with a pedestrian; 
         FIG. 5  is a schematic perspective view of the arrangement of the first embodiment according to the present invention mounted on a vehicle; 
         FIG. 6  is a schematic perspective view corresponding to  FIG. 5 , though illustrating a further embodiment. 
         FIG. 7A  is a schematic sectional view of a second embodiment of an impact energy transmitting arrangement according to the present invention with the arrangement in its non-influenced condition; 
         FIG. 7B  is a schematic sectional view corresponding to  FIG. 7A , though with the arrangement in a condition after a typical low speed impact; 
         FIG. 7C  is a schematic sectional view corresponding to  FIG. 7A , though with the arrangement in a condition after a typical impact with a pedestrian; 
         FIG. 7D  is a schematic sectional view corresponding to  FIG. 7A , though with the arrangement in a condition after a typical high speed impact; 
         FIG. 8  is a schematic sectional view through the housing of the second embodiment of the impact energy transmitting arrangement; 
         FIG. 9  is a schematic perspective view of a third embodiment of an impact energy transmitting arrangement according to the present invention; 
         FIG. 10A  is a schematic plan corresponding to  FIG. 9  with the arrangement in its non-influenced condition; 
         FIG. 10B  is a schematic plan view corresponding to  FIG. 10A , though with the arrangement in a condition after a typical low speed impact, and 
         FIG. 10C  is a schematic plan view corresponding to  FIG. 10A , though with the arrangement in a condition after a typical impact with a pedestrian. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the drawings constituted by  FIGS. 1  to  6 , reference numeral  10  generally denotes an impact energy transmitting arrangement in accordance with a first embodiment of the present invention. As illustrated in  FIG. 5 , the arrangement  10  is intended to be mounted on a vehicle, generally denoted by  12 , so as to transmit energy which arises during an impact between the vehicle and a foreign body to the vehicle structure  14 . In this respect, the vehicle structure  14  is generally a part of a deformation zone at the front of the vehicle and may comprise a longitudinally extending progressively deformable beam  16  adapted to absorb energy during an impact. 
     In the following description, the expression “foreign body” encompasses any object remote from the vehicle with which the vehicle may impact. Thus, the foreign body may be constituted by another vehicle, a pedestrian, a building, a lamppost or signpost, an animal, a tree or any other movable or immovable object. 
     With particular reference to  FIGS. 1 and 2 , the impact energy transmitting arrangement  10  of a first embodiment of the present invention comprises a first means  18  which is displaceable in a first direction denoted by arrow A in  FIG. 1 , and second means  20  adapted for co-operation with the first means. The first and second means are arranged in a housing  22  which thereby defines a self-contained unit which may be mounted on a vehicle in the manner illustrated in FIG.  5 . In a preferred embodiment, the second means is arranged for displacement in a second direction substantially perpendicular to the first direction. To facilitate displacement of the first and second means, the housing  22  may be provided with a first guide portion  24  extending in the first direction and a second guide portion  26  extending in the second direction. 
     The first means  18  is shown in greater detail in FIG.  3 . Thus, the first means  18  is constituted by an elongate member  28  having a longitudinal extension along a longitudinal axis  30  in the first direction, i.e. the direction of its intended displacement. The elongate member  28  may have any suitable cross-sectional shape, though it is preferably circular. In order to function optimally, the inertia of the elongate member should be as low as possible. Hence, it is advantageous if the elongate member is in the form of a tube made from lightweight material. Irrespective of its actual shape, the elongate member presents a transverse extension in the second direction. Along its longitudinal axis  30 , the elongate member has a first region  32  having a first transverse dimension  34  in the second direction and a second region  36  having a second transverse dimension  38  in the second direction. The second transverse dimension is less than said first transverse dimension. A third region  40  is provided between the first and second regions. The third region has a minimum third transverse dimension  42  in the second direction which is less than the second transverse dimension  38 . The third region  40  abuts the second region  36  at a location at which the third region has its minimum third transverse dimension  42  such that an abutment shoulder  44  is formed. The third region  40  also abuts the first region at a location  46  at which the third region has a maximum third transverse dimension having a value substantially equal to the first transverse dimension  34  of the first region  32 . Advantageously, the third region  40  has a surface  48  which tapers from the maximum to the minimum third transverse dimension along a first distance in the first direction. The first region  32  extends a distance along the longitudinal axis  30  sufficient to allow the first guide portion  24  of the housing (see  FIG. 2 ) to guide the elongate member  28  during at least its initial displacement in the first direction. 
     The second means  20  will now be described with particular reference to  FIGS. 4A  to  4 C. 
     The second means  20  comprises at least one abutment member  50  having a first end  52  and a second end  54 . In the illustrated preferred embodiment, two opposed abutment members are provided. For the sake of clarity, reference will be made in the following to just one of the abutment members, though it is to be understood that the abutment members are identical. The abutment member  50  is disposed in the second guide portion  26  of the housing  22  such that its first end  52  is proximal the elongate member  28 . The second end  54  of the abutment member is influenced by resilient means such as a helical spring  56  to bias the abutment member towards the elongate member  28 . In a manner which will be described in greater detail in the following, the helical spring  56  urges the second means in the form of the abutment member  50  at a predetermined rate of acceleration towards the first means  18 . 
     In a non-influenced condition, i.e. before impact, of the arrangement  10 , and as illustrated in  FIG. 4A , the first end  52  of the abutment member  50  abuts against the first region  32  of the elongate member at a location substantially corresponding to the location  46  at the intersection between the first and third regions of the elongate member. Preferably, the first end  52  of the abutment member is chamfered such that it presents an angle substantially corresponding to the angle of taper of the surface  48  of the third region  40  of the elongate member  28 . Accordingly, the first end presents a surface  58  which is substantially parallel to the surface  48  of the third region. 
     The first embodiment of the impact energy transmitting arrangement of the present invention is designed to be operable in the following manner. 
     The arrangement  10  is illustrated in  FIG. 4A  in its non-influenced condition, i.e. before impact between the vehicle upon which it is mounted and a foreign body. The first region  32  of the elongate member projects into the first guide portion  24  of the housing  22 . As previously mentioned, the first end  52  of the abutment member  50  abuts against the first region  32  of the elongate member at a location substantially corresponding to the location  46  at the intersection between the first and third regions of the elongate member. 
     If the vehicle to which the arrangement  10  is mounted is involved in a low speed collision with a foreign body, for example the velocity of the vehicle is below 30 km/h, preferably below 20 km/h and is most preferably about 15 km/h, the arrangement will be caused to adopt the condition illustrated in FIG.  4 B. Thus, upon impact, the elongate member  28  is caused to accelerate along the first guide portion  24  past the first end  52  of the abutment member  50 . Due to the relatively low quantity of energy which arises during such a low speed impact, the rate of acceleration of the elongate member will be such that the helical spring  56  maintains the first end  52  of the abutment member  50  in contact with the elongate member. Accordingly, the surface  58  of the first end of the abutment member slides over the tapered surface  48  of the third region  40  of the elongate member until the abutment member is caused to abut against the abutment shoulder  44  on the elongate member. In this condition, further displacement of the elongate member  28  in the first direction is prevented and the arrangement presents a first resistance-to-displacement value. 
     If the vehicle to which the arrangement  10  is mounted is involved in a somewhat higher speed collision with a foreign body, such as a pedestrian, for example the velocity of the vehicle is up to about 60 km/h, the arrangement will be caused to adopt the condition illustrated in FIG.  4 C. Again, upon impact, the elongate member  28  is caused to accelerate along the first guide portion  24  past the first end  52  of the abutment member  50 . Due to the higher speed of impact compared with the  FIG. 4B  scenario, the rate of acceleration of the elongate member will also be higher. By appropriate selection of i.a. the biasing force applied to the abutment member  50  by the helical spring  56 , the abutment member  50  will be caused to accelerate at a predetermined rate towards the elongate member  28  such that before the first end of the abutment member has travelled a distance corresponding to the difference between the first transverse dimension  34  of the elongate member and the second transverse dimension  38 , the elongate member has travelled along the first guide portion  24  of the housing  22  a distance greater than the extension of the third region  40  of the elongate member. This implies that the abutment shoulder  44  will travel past the first end  52  of the abutment member without the abutment member having made contact with the third region of the elongate member. As such, the abutment member will be caused to abut against the second region  36  of the elongate member and continued displacement of the elongate member through the first guide portion of the housing will not be hindered by the abutment member. In this condition, the arrangement presents a second resistance-to-displacement value which is considerably lower than the first resistance-to-displacement value attained in the  FIG. 4B  condition. 
     In a non-limiting embodiment of the invention the distance corresponding to the difference between the first transverse dimension  34  of the elongate member and the second transverse dimension  38  may be about 5 mm and the extension of the third region  40  of the elongate member along the longitudinal axis  30  may be about 20 mm. 
     In a preferred embodiment of the invention, and as is schematically illustrated in  FIG. 4B , the arrangement  10  may be provided with return means  60  acting on the elongate member  28  to return the arrangement to its non-influenced condition corresponding to FIG.  4 A. The return means  60  may be constituted by a spring or may comprise hydraulic or pneumatic means. 
     In order that vehicle deformation zones shall function adequately during high speed collisions, an arrangement which is stiffer than that for optimal pedestrian injury reduction is required. Thus, in accordance with an preferred embodiment, the first means and second means are operable such that, as a result of an impact between the vehicle and a foreign body for which the energy to be transmitted is above a second predetermined value, the arrangement is stiffer than it would be as a result of an impact for which the energy to be transmitted is below the second predetermined value. The second predetermined value may correspond to a velocity above 40 km/h, preferably above 50 km/h and is most preferably about 60 km/h. This may be attained by providing the arrangement  10  with actuable retarding means  62  for retarding the displacement of the elongate member  28  through the first guide portion  24  of the housing. In  FIG. 4A  the actuable retarding means  62  is schematically illustrated as a constricting ring located around the first guide portion slightly downstream of the first region of the elongate member  28  when the arrangement  10  is in its non-influenced condition. Upon impact with a foreign body at a velocity above a predetermined value, the actuable retarding means  60  is actuated, for example by a speed-dependent sensor, to constrict the first guide portion  24 , thereby retarding the elongate member  28 . Thus, the elongate member is caused to accelerate past the first end  52  of the abutment member  50  at a rate such that the abutment member is caused to abut against the abutment shoulder  44  in a manner similar to that explained above with respect to FIG.  4 B. 
     A second embodiment of the present invention will now be described with particular reference to  FIGS. 7A  to  7 D and FIG.  8 . In these drawings, reference numeral  70  generally denotes the impact energy transmitting arrangement of the second embodiment of the present invention. The first means is denoted by  72  and the second means by  74 . In common with the first embodiment, the first and second means are arranged in a housing  76  which thereby defines a self-contained unit which may be mounted on a vehicle in a similar manner to that illustrated in FIG.  5 . In contrast to the first embodiment in which the first and second means are not joined, in the second embodiment the second means  74  is carried by the first means  72  in a manner which is described below. 
     Thus, the first means  72  is constituted by an elongate member  78  having a longitudinal extension along a longitudinal axis  80  in the first direction, i.e. the direction of its intended displacement. The elongate member  78  may have any suitable cross-sectional shape, though it is preferably circular. In order to function optimally, the inertia of the elongate member should be as low as possible. Hence, it is advantageous if the elongate member is in the form of a tube made from lightweight material such as aluminium or plastic. The elongate member  78  comprises two distinct portions, namely a first portion  82  arranged to be located substantially within the housing  76  when the arrangement  70  is in its non-influenced condition, and a second portion  84  projecting out of the housing in the non-influenced condition of the arrangement. The second portion  84  has a distal end  86  which is intended to receive the initial impact in the event of a collision, and a proximal end  88  adjacent the first portion  82 . In the drawings, the first and second portions have been illustrated as two separate components joined together to form the elongate member  78 . However, it is to be understood that it is within the scope of the present invention that the elongate member  78  be made in one piece. 
     The first portion  82  has a proximal end  90  having a first transverse dimension  92 , i.e. an extension in the direction perpendicular to the longitudinal axis  80 . The proximal end  90  lies adjacent the proximal end  88  of the second portion  84 . To permit the elongate member  78  to be displaceable within the housing  76 , the first transverse dimension  92  must be at least as great as the transverse dimension of the second portion  84  over the portion of the second portion which has to be able to pass through the housing. The first portion  82  has a distal end  94  which advantageously has a second transverse dimension  96  which is greater than the first transverse dimension  92 . Between its proximal end  90  and its distal end  94 , the first portion  82  of the elongate member has an intermediate portion  98  having a transverse dimension which is less than the first transverse dimension  92 . The intermediate portion  98  is arranged to carry the second means  74 . 
     Thus, the second means  74  is constituted by at least one pivotal abutment member  100 . The abutment member  100  has an extension in the direction of the longitudinal axis  80  and is pivotally mounted to the intermediate portion  98  of the first portion  82  of the elongate member  78  about a pivot axis  102  approximately mid way along the abutment member. Preferably, the pivot axis  102  extends perpendicular to the longitudinal axis  80 . The abutment member  100  has a first abutment end  104  and a second abutment end  106 . In a manner which will be explained in greater detail below, the first and second abutment ends are adapted to co-operate with recesses in the housing  76 . 
     The housing  76  is shown most clearly in FIG.  8  and has an inner mantle surface  107  delimiting a through hole. Along the longitudinal axis  80 , the though hole has a first region  108  having a first longitudinal dimension  110  and a first transverse dimension  112 . The through hole further has a second region  114  having a plurality of second longitudinal dimensions  116 . In the second region  114 , the second transverse dimensions of the through hole vary, but are always greater than the first transverse dimension  112 . 
     The first region  108  is provided with a first abutment surface  118 . In the illustrated embodiment, the first abutment surface  118  is formed by a portion of a first recess  120  in the inner mantle surface  107  of the housing. It is to be understood, however, that the first abutment surface may instead be constituted by the end face  122  of the housing  76 . The second region  114  of the through hole has a second abutment surface  124  formed by a portion of a second recess  126  in the inner mantle surface  107  of the housing. The second recess has a tapering surface  128  terminating at a point at which the second transverse dimension of the through hole is a maximum. The second abutment surface  124  is then formed by a region of lesser transverse dimension  127  than the maximum second transverse dimension. Advantageously, the first and second abutment surfaces  118 ,  124  form an acute angle with respect to the longitudinal axis  80  such that undercuts are formed in the housing. 
     Referring back to  FIG. 7A , it will be noted that the pivotal abutment member  100  is influenced by a biasing member which, and as illustrated, may be constituted by a spring  130 . The spring  130  is arranged with respect to the elongate member  78  and the abutment member such that the second abutment end  106  of the abutment member is continuously biased towards the inner mantle surface  107  of the housing. In the non-influenced condition of the arrangement  70 , the second abutment end  106  abuts the inner mantle surface  107  substantially at the intersection between the first region  108  and the second region  114  of the through hole of the housing, i.e. at the commencement of the tapering surface  128 . When two pivotal abutment members  100  are utilised, the spring  130  may advantageously be arranged to act on both members simultaneously by locating the spring  130  in a through hole  132  in the intermediate portion  98  of the first portion  82  of the elongate member  78 . 
     The second embodiment of the impact energy transmitting arrangement of the present invention is designed to be operable in the following manner. 
     The arrangement  70  is illustrated in  FIG. 7A  in its non-influenced condition, i.e. before impact between the vehicle upon which it is mounted and a foreign body. It is to be noted that there is a distance  134  defining a gap between the first abutment end  104  of the abutment member  100  and the first abutment surface  118  of the first recess  120  in the housing  76 . 
     If the vehicle to which the arrangement  10  is mounted is involved in a collision in which the energy which arises is relatively low, for example for a typical the low speed collision of the vehicle with a pedestrian with the velocity of the vehicle being below 30 km/h, preferably below 20 km/h and being most preferably about 15 km/h, the arrangement will be caused to adopt the condition illustrated in FIG.  7 B. Thus, upon impact, the elongate member  78  is caused to accelerate in the direction of arrow A through the housing  76 . Due to the relatively low quantity of energy which arises during such a low speed impact, the rate of acceleration of the elongate member will be such that the spring  130  maintains the second abutment end  106  of the abutment member  100  in contact with the inner mantle surface  107  formed by the second recess  126 . Accordingly, the second abutment end  106  of the abutment member slides over the tapering surface  128  of the housing. Since the spring  130  effects pivotal displacement of the abutment member about the pivot axis  102  during displacement of the elongate member  78 , the first abutment end  104  of the abutment member will be withdrawn from the first recess  120 . This implies that the elongate member may continue its displacement until the second abutment end  106  of the abutment member abuts against the second abutment surface  124  in the second region  114  of the through hole of the housing. In this condition, further displacement of the elongate member  78  in the first direction is prevented and the arrangement presents a first resistance-to-displacement value. 
     If the vehicle to which the arrangement  70  is mounted is involved in a somewhat higher speed collision with a foreign body, such as a pedestrian, for example the velocity of the vehicle is up to about 60 km/h, the arrangement will be caused to adopt the condition illustrated in FIG.  7 C. Again, upon impact, the elongate member  78  is caused to accelerate in the direction of arrow A through the housing  76 . Due to the higher amount of energy which arises in such an impact compared with the  FIG. 7B  scenario, the rate of acceleration of the elongate member will also be higher. By appropriate selection of i.a. the biasing force applied to the abutment member  100  by the spring  130 , the second abutment end  106  of the abutment member will be caused to accelerate at a predetermined rate towards the inner mantle surface of the second recess  126  such that, before the first end of the abutment member has travelled a distance in the transverse direction corresponding to half the difference between the lesser transverse dimension  127  and the first transverse dimension  112  of the housing, the elongate member has travelled a distance greater than the longitudinal extension of the second recess  126 . This implies that the second abutment end  106  of the abutment member  100  will travel past the second abutment surface  124  of the second recess  126  of the housing without the second abutment end  106  having made contact with the inner mantle surface of the second recess. As such, continued displacement of the elongate member  78  through the housing  76  will not be hindered by the abutment member. In this condition, the arrangement presents a second resistance-to-displacement value which is considerably lower than the first resistance-to-displacement value attained in the  FIG. 7B  condition. 
     As with the first embodiment, the arrangement  70  may be provided with return means  136  acting on the elongate member  78  to return the arrangement to its non-influenced condition corresponding to FIG.  7 A. The return means  136  may be constituted by a spring or may comprise hydraulic or pneumatic means. 
     In accordance with a preferred embodiment, the first means  72  and second means  74  are operable such that, as a result of an impact between the vehicle and a foreign body for which the energy to be transmitted is above a second predetermined value, the arrangement is stiffer than it would be as a result of an impact for which the energy to be transmitted is below the second predetermined value. The second predetermined value may correspond to a velocity above 40 km/h, preferably above 50 km/h and is most preferably about 60 km/h. This is attained by suitable selection of the distance  134  defining the gap between the first abutment end  104  of the abutment member  100  and the first abutment surface  118  of the first recess  120  in the housing  76  when the arrangement  70  is in its non-influenced condition. Due to the high amount of energy which arises in e.g. a high speed collision, the elongate member  78  will be accelerated at a high rate. This implies that, and as is illustrated in  FIG. 7D , the elongate member  78  will cover the above-defined distance  134  before the second abutment end  106  of the abutment member has had time to be displaced in the radial displacement a distance corresponding to the distance of projection of the first abutment end  104  of the abutment member into the first recess  120 . This implies that the first abutment end  104  will be brought into abutment with the first abutment surface  118  of the first recess  120 . In this condition, further displacement of the elongate member  78  in the first direction is prevented and the arrangement presents a third resistance-to-displacement value which is considerably greater than the second resistance-to-displacement value. 
     In the first and second embodiments described above, the first means  18 ,  72  undergo a substantially rectilinear displacement in the first direction. A third embodiment will now be described in which the first direction is a direction of rotation, i.e. the displacement is a rotational displacement. 
     Thus, with reference to FIG.  9  and  FIGS. 10A  to  10 C, reference numeral  140  generally denotes the impact energy transmitting arrangement of the third embodiment of the invention. The first means is denoted by  142 , and the second means by  144 . The first means is constituted by a pivotal member  146  arranged to be pivotally mounted to a structural component  148  of a vehicle at a pivot point  150 . When the pivotal member  146  is arranged at the front of a vehicle, the pivotal member  146  presents a forward impact region  152  which, in the non-influenced condition of the arrangement as shown in  FIG. 9 , projects beyond the pivot point  150  seen in the direction of forward travel of the vehicle. In other words, if the vehicle were to be involved in a frontal collision with a foreign object, the forward impact region  152  of the pivotal member would receive the impact first. In the illustrated embodiment, the pivotal member  146  has a generally L-shaped form in plan view. However, it is to be understood that any shape may be employed which provides for a forward impact region which is forwardly displaced with respect to the pivot point of the pivotal member. For example, the pivotal member  146  may be triangular shaped in plan view. The pivotal member  146  is illustrated as comprising a pair of L-shaped members joined by a bridging member  154 , with the bridging member corresponding to the forward impact region  152 . The skilled person will recognise, nevertheless, that the pivotal member may instead be solid or may be constituted by a single generally two dimensional pivotal member. 
     The illustrated L-shaped pivotal member  146  has a first arm  156  and a second arm  158 . The first arm has a first end  160  which accommodates the pivot point  150  and a second end  162 . The second arm has a free first end  164  and a second end  166  which co-operates with the second end  162  of the first arm  156  to constitute the forward impact region  152 . The expression “co-operates” is hereby intended to encompass all forms of co-operation between the two arms. Such co-operation may be due to the fact that the L-shaped pivotal member is made in one piece such that one arm is a continuation of the other, or that the L-shaped pivotal member is fabricated from a plurality of parts such that the two arms are joined together by a suitable joint. In the illustrated embodiment, the first arm  156  is generally straight and the second arm  158  is curved. However, it is to be understood that the two arms may have any shape which will permit the arrangement to function in the manner to be described below. 
     It will be apparent that if the pivotal member  146  is subjected to an impact force, it will tend to rotate about the pivot point  150  such that the second arm  158  follows a first, radial, direction indicated by arrow B. 
     The second arm  158  has a first surface  168  directed radially away from the pivot point  150 . Towards the free first end  164  of the second arm  158 , a recess  170  is provided in the first surface  168 . On the side of the recess towards the free first end  164 , the second arm is provided with a projecting portion  172  terminating at a region which is at a maximum distance from the pivot point  150 . This implies that the recess  170  is delimited by a longer surface  174  towards the free first end  164  of the second arm  158  and a shorter surface constituting an abutment surface  176  towards the second end  166  of the arm (see FIG.  10 A). The recess  170  is angled with respect to the second arm such that the abutment surface  176  delimits an undercut in the arm. The dimensions of the recess  170  are selected such that the recess may accommodate the second means  144 , as described in detail below. 
     The second means  144  of the impact energy transmitting arrangement  140  is constituted by an abutment member  178 . As is schematically depicted, the abutment member  178  is biased by suitable spring means  180  towards the first surface  168  of the second arm. In other words, the abutment member is urged to accelerate towards the pivotal member  146  at a predetermined rate. In the non-influenced condition of the arrangement, the spring means  180  ensures that the abutment member  178  abuts the first surface  168  where it may be accommodated in a resting hollow  182  in the projecting portion  172  of the second arm  158 . The abutment member  178  is illustrated as an elongate pin, though it is to be understood that any suitable shape of member may employed. 
     The third embodiment of the impact energy transmitting arrangement of the present invention is designed to be operable in the following manner. 
     The arrangement  140  is illustrated in  FIG. 10A  in its non-influenced condition, i.e. before impact between the vehicle upon which it is mounted and a foreign body, with the abutment member  178  being accommodated in the resting hollow  182  in the second arm  158  of the pivotal member  146 . If the vehicle to which the arrangement  140  is mounted is involved in a low speed collision with a foreign body, for example the velocity of the vehicle is below 30 km/h, preferably below 20 km/h and is most preferably about 15 km/h, the arrangement will be caused to adopt the condition illustrated in FIG.  10 B. Thus, upon impact, the pivotal member  146  is caused to accelerate about the pivot point  150 . Due to the relatively low quantity of energy which arises during such a low speed impact, the rate of acceleration of the pivotal member will be such that the spring  180  maintains the abutment member  178  in contact with the first surface  168  of the second arm  158  of the pivotal member  146 . Accordingly, the abutment member  178  slides over the longer surface  174  of the recess  170  until the abutment member is caused to abut against the abutment surface  176  of the recess. In this condition, further displacement of the pivotal member  146  in the first direction B is prevented and the arrangement presents a first resistance-to-displacement value. 
     If the vehicle to which the arrangement  140  is mounted is involved in a somewhat higher speed collision with a foreign body, such as a pedestrian, for example the velocity of the vehicle is up to about 60 km/h, the arrangement will be caused to adopt the condition illustrated in FIG.  10 C. Again, upon impact, the pivotal member  146  is caused to accelerate about the pivot point  150 . Due to the higher speed of impact compared with the  FIG. 10B  scenario, the rate of acceleration of the pivotal member will also be higher. By appropriate selection of i.a. the biasing force applied to the abutment member  178  by the spring  180 , the abutment member  178  will be caused to accelerate at a predetermined rate towards the second arm  158  of the pivotal member  146  such that before the abutment member has travelled a distance corresponding to the difference between the radial extremity of the longer surface  174  and that of the shorter surface constituting the abutment surface  176 , the pivotal member has rotated about the pivot point  150  an angle corresponding to a distance greater than the radial extension of the recess  170  of the pivotal member. This implies that the recess  170  will travel past the abutment member without the abutment member having made contact with the abutment surface  176  of the recess. As such, continued displacement of the pivotal member  146  will not be hindered by the abutment member  178 . In this condition, the arrangement presents a second resistance-to-displacement value which is considerably lower than the first resistance-to-displacement value attained in the  FIG. 10B  condition. 
     In a preferred embodiment of the invention, and as is schematically illustrated in  FIGS. 10A and 10B , the arrangement  140  may be provided with return means  184  acting for example between the structural component  148  and the pivotal member  146  to return the arrangement to its non-influenced condition corresponding to FIG.  10 A. The return means  184  may be constituted by a spring or may comprise hydraulic or pneumatic means. In a non-illustrated embodiment, the return means may be a spiral spring acting on the pivotal member about the pivot point  150 . 
     In order that vehicle deformation zones shall function adequately during high speed collisions, an arrangement which is stiffer than that for optimal pedestrian injury reduction is required. Thus, in accordance with an preferred embodiment, the first means and second means are operable such that, as a result of an impact between the vehicle and a foreign body for which the energy to be transmitted is above a second predetermined value, the arrangement is stiffer than it would be as a result of an impact for which the energy to be transmitted is below the second predetermined value. The second predetermined value may correspond to a velocity above 40 km/h, preferably above 50 km/h and is most preferably about 60 km/h. This may be attained in a similar manner to the first embodiment by providing the arrangement  140  with actuable retarding means  186  for retarding the displacement of the pivotal member  146 . In  FIG. 10A  the actuable retarding means  186  is schematically illustrated as a blocking element arranged to be displaced in a radial direction towards the projecting portion  172  of the first free end  164  of the second arm  158  of the pivotal member  146 . Upon impact with a foreign body at a velocity above a predetermined value, the actuable retarding means  186  is actuated, for example by a speed-dependent sensor, to displace the blocking element into the path of the second arm  158 , thereby retarding the pivotal member  146 . Thus, the pivotal member is caused to accelerate past the abutment member  178  at a rate such that the abutment member is caused to abut against the abutment surface  176  in a manner similar to that explained above with respect to FIG.  10 B. 
     In order to further reduce risk of pedestrian injury, the arrangements  10 ,  70 ,  140  of the present invention may be used together with a pedestrian impact energy absorber  64  as illustrated in FIG.  6 . The pedestrian impact energy absorber  64  is a relatively soft component arranged transversely across the front of the vehicle  12 . The absorber  64  may be covered by a (not shown) substantially rigid panel carried by the first means  18  of the impact energy transmitting arrangement  10 ,  70 ,  140  of the present invention. If a pedestrian is struck by the vehicle when the vehicle is travelling at a velocity corresponding to e.g. the  FIG. 4C  scenario, the impact energy will be transmitted by the substantially rigid panel to the arrangement, thereby causing the elongate member  28  to adopt the position shown in FIG.  4 C. This implies that the substantially rigid panel will strike the pedestrian impact energy absorber  64 , thereby effecting gentle absorption of the impact energy. 
     Although the arrangement according to the invention has been termed an impact energy transmitting arrangement, it is to be understood that the use of this term does not exclude the arrangement from absorbing some energy which arises during impact between the vehicle and a foreign body. 
     The invention has been described above and illustrated in the drawings by way of example only and the skilled person will recognise that various modifications may be made without departing from the scope of the invention as defined by the appended claims.