Abstract:
A child safety seat comprises a seat structure having a base support surface for resting on a vehicle seat cushion, and a seating surface for a child occupant, the seating surface. A rigid link is attached to the child seat structure solely by a coupling mechanism that permits angular movement of the child seat structure relative to the rigid links about an axis located above the base support surface. A releasable connector is mounted on the rigid link for engagement with a standard anchorage unit associated with the vehicle seat. The child safety seat may be either forward facing or rearward facing.

Description:
[0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 09/678,004. 
     
    
     FIELD  
       [0002]     This invention relates to a child safety seat for use in a vehicle.  
       RELATED ART  
       [0003]     It is well known for a child safety seat to rest on a vehicle seat and to be secured thereon by the corresponding vehicle seat belt. The disadvantage of this arrangement is that, even if the vehicle seat belt is pulled very tight during installation, the resilience of the belt, will permit undesirable movement of the child seat relative to the vehicle in the event of sudden deceleration, for example, during an accident. In order to overcome this disadvantage, it has been proposed to provide vehicle seats with standard anchorage units at agreed locations for engagement by releasable connectors which are attached to the child seat structure by rigid links. Such anchorage units will be referred to hereinafter as “standard anchorage units”.  
         [0004]     The invention relates to a child safety seat of the type comprising a child seat structure having a base support surface for resting on a vehicle seat cushion, a back support surface for abutting against the seat back of said vehicle seat, a rigid link projecting from the child seat structure between the base support surface and the back support surface, and a releasable connector mounted on the rigid link for engagement with a standard anchorage unit associated with the vehicle seat.  
         [0005]     U.S. Pat. No. 6,082,819 discloses such a child safety seat for use with two standard anchorage units located near the rear edge of the vehicle seat cushion and the bottom of the vehicle seat back. This arrangement is subject to the disadvantage that, in the event of an accident, the child seat tends to rotate about the standard anchorage units, compressing the front part of the vehicle seat cushion and allowing undesirable forward movement of the head of a child occupant of the child seat. The present invention aims to provide a child safety seat in which this disadvantage is mitigated.  
       SUMMARY OF THE INVENTION  
       [0006]     According to the invention, in a child safety seat of the type described above, the rigid link is pivotally attached to the child seat structure.  
         [0007]     Preferably the rigid link is pivotally attached to the child seat structure at a pivot location above the base support surface.  
         [0008]     In the event of sudden deceleration, operation of this arrangement differs from the prior art in that the centre of gravity of the combination of the child seat structure and the seat occupant does not rotate about the standard anchorage units at a constant radius. Instead both the front and rear edges of the base support surface are pressed downwards into the vehicle seat cushion simultaneously. This results in a reduction in the distance of this centre of gravity from the anchorage units and therefore a corresponding reduction in the rotational moment exerted by the inertia of the child seat. The overall result is a reduction of the extend of forward excursion of the child&#39;s head.  
         [0009]     Preferably, each rigid link is L-shaped with a first limb carrying the corresponding connector and a second limb having its free end pivotally attached to the child seat structure. In normal use, the first limb lies in a rearward continuation of the plane of the base support surface and the second limb is generally parallel to the back support surface.  
         [0010]     The height of the pivot location above the base surface is at least 30 mm so as to be greater than the reduction of the thickness of the vehicle seat cushion when it is fully compressed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a perspective view of a vehicle seat equipped with standard anchorage units;  
         [0012]      FIG. 2  is a schematic side view of a known forward-facing child seat installed on the vehicle seat shown in  FIG. 1  with a test dummy on the child seat;  
         [0013]      FIG. 3  is a side view similar to  FIG. 2  showing the child seat and dummy in an initial phase of movement after sudden deceleration of the vehicle;  
         [0014]      FIG. 4  is a schematic side view, similar to  FIGS. 2 and 3  after a second phase of deceleration;  
         [0015]      FIGS. 5, 6  and  7  are side views, similar to  FIGS. 2, 3  and  4  respectively showing a forward-facing child seat in accordance with the invention on the vehicle seat shown in  FIG. 1 ;  
         [0016]      FIG. 8  is a schematic side view of a known rearward facing child seat installed on the vehicle seat shown in  FIG. 1  with a test dummy on the child seat;  
         [0017]      FIG. 9  is a side view similar to  FIG. 2  showing the child seat and dummy after an initial phase of sudden deceleration of the vehicle;  
         [0018]      FIGS. 10 and 11  are schematic side views, similar to  FIGS. 8 and 9  of a first rearward-facing embodiment of the invention;.  
         [0019]      FIG. 12  is a schematic side view of the embodiment shown in  FIGS. 10 and 11 , after a second phase of deceleration;  
         [0020]      FIGS. 13 and 14  are schematic side views, similar to  FIGS. 10 and 11  of a second rearward-facing embodiment of the invention;  
         [0021]      FIGS. 15 and 16  are schematic side views, similar to  FIGS. 10 and 11  of a third rearward-facing embodiment of the invention;  
         [0022]      FIGS. 17 and 18  are schematic side views, similar to  FIGS. 10 and 11  of a fourth rearward-facing embodiment of the invention; and  
         [0023]      FIGS. 19 and 20  are schematic side views, similar to  FIGS. 10 and 11  of a fifth rearward-facing embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]      FIG. 1  shows a vehicle seat  10  equipped with two standard anchorage units according to the first proposal. The seat  10  comprises a seat cushion  12  and a backrest  14 . The two standard anchorage units comprise transversely extending rods  16  and  18  which are accessible through openings  20  and  22  in the bottom of the backrest and which are rigidly secured to the frame (not shown) of the seat  10 .  
         [0025]      FIG. 2  shows a known child seat  30  having a base support surface  32  resting on the seat cushion  12  of the vehicle seat  10  and a back support surface  34  abutting against the backrest  14 . A rigid link  36  projects from the junction between the base support surface  32  and the back support surface  34  and is rigidly secured to the child seat  30  so as to be fixed parallel with the base support surface  32 . A releasable connector  38  engages with the standard anchorage unit  16 . A similar releasable connector (not shown), on another rigid link, engages with the other standard anchorage unit  18 . The releasable connectors may be as described in U.S. Pat. No. 6,082,819.  
         [0026]     The seat is occupied by a test dummy  40  having a reference marking  42  on the side of its head. The dummy  40  is retained on a seating surface  43  of the child seat  30  by a conventional harness (not shown).  
         [0027]     If the vehicle seat  10  is subject to sudden deceleration in the normal direction of travel, the child seat  30  tends to pivot in the counter-clockwise direction (as viewed in FIGS.  2  to  4 ) about the standard anchorage units  16  and  18 . This results in compression of the part  44  of the vehicle seat cushion  12  which is under the front edge of the base surface  32  and pivotal movement of the child seat  30  through an angle β as shown in  FIG. 3 . During the next phase of movement, the torso of the dummy  40  pivots about its pelvis through an angle α as shown in  FIG. 4 , resulting in a total forward movement through an angle δ (equal to α+β). This movement allows the head of the dummy to come into contact with a reference surface  46  positioned in front of the vehicle seat  10 , thus exceeding the extent of undesirable forward movement.  
         [0028]      FIG. 5  shows a child seat  50  in accordance with the invention, having support surfaces  32  and  34  similar to the correspondingly numbered support surfaces of the child seat  40 . However, the releasable connector  38 , which engages with the standard anchorage unit  16  is mounted on the end of one limb  52  of an L-shaped link, the other limb  54  of which has its free end attached by a pivot connection  56  to the child seat  50  at a location adjacent to the back support surface  34  above the base support surface  32  at a distance equal to the length of the limb  54 . A similar link (not shown) is provided for the connector which engages with the other standard anchorage unit  18 .  
         [0029]     Under normal conditions, the link  52 ,  54  is retained in the orientation shown in  FIG. 5  by a latch (not shown), such as ball catch which is designed to release when a load is applied. During the first phase of forward movement in the event of sudden deceleration, the link  52 ,  54  pivots in the counter-clockwise direction about the standard anchorage unit  16 ′. The pivot joint  56  allows the base support surface  32  of the seat  50  to remain generally parallel to the vehicle seat cushion  12 , compressing it substantially uniformly, as shown in  FIG. 6 . Consequently, the effective range of angular movement of the child seat  50  about the standard anchorage unit  16  is limited to ε, which is substantially less than β. The compression of such a large area of the vehicle seat cushion  12  provides a greater resistance against downward movement of the child seat  50 , with the result that the front edge of the base support surface  32  is higher in  FIG. 6  than in  FIG. 3 .  
         [0030]     During the subsequent phase of movement, the torso of the dummy  40  pivots about its pelvis through the angle α, as before. The total angular movement θ of the dummy  40  is less than the angle δ, as shown in  FIG. 7 . Consequently, the total forward movement of the head of the dummy  40  is less, leaving a clearance a from the reference surface  46 , as shown in  FIG. 7 .  
         [0031]      FIG. 8  shows a known rearward facing child seat  130  having a base support surface  132  resting on the seat cushion  12  of the vehicle seat  10 . A rigid link  136  projects rearwardly just above the base support surface  132  and is rigidly secured to the child seat  130  so as to be fixed parallel with the base support surface  132 . A releasable connector  138  engages with the standard anchorage unit  16 . A similar releasable connector (not shown), on another rigid link, engages with the other standard anchorage unit  18 . The seat is occupied by a test dummy  140  having a reference mark  142  on the side of its body near its centre of gravity. The dummy  140  is retained in the child seat  130  by a conventional harness (not shown).  
         [0032]     If the vehicle seat  10  is subject to sudden deceleration in the normal direction of travel, the child seat  130  tends to pivot in the counter-clockwise direction (as viewed in  FIGS. 8 and 9 ) about the standard anchorage units  16  and  18 . This results in compression of the part  144  of the vehicle seat cushion  12  which is under the front edge of the base surface  132  and pivotal movement of the child seat  130  as shown in  FIG. 9 , causing a decrease of the angle {acute over (α)} between the normal position of the top surface  146  of the vehicle seat cushion  12  and the backrest  148  of the child seat  130 . The reference mark  142  moves forwards through a distance L from its original position (shown at  142   a  in  FIG. 9 ) to an new position  142   b.  This movement allows the head of the dummy to come into contact with a reference surface  149  positioned in front of the vehicle seat  10 , thus exceeding the extent of acceptable forward movement.  
         [0033]      FIG. 10  show a child seat  150  in accordance with the invention. The links  132  are replaced by longer links  152  which are attached by pivot joints  154  to side wings  156  of the child seat  150  in the vicinity of the head of the dummy  140 , i.e. well above the centre of gravity of the child seat  150  and the dummy  140 . Releasable connectors  138  are mounted on the other ends of the links  152  and engage with respective anchorage units  16  and  18 .  
         [0034]     During sudden deceleration, the child seat  150  pivots in a clockwise direction about the pivot joints  154  resulting in an increase in the angle {acute over (α)}. Consequently, although the reference mark  142  still moves forwards through approximately the same distance L, a substantial clearance a remains between the head of the dummy  140  and the reference surface  149 .  
         [0035]     After its initial phase of movement, the child seat  150  is subject to rebound. Counter-clockwise angular movement of the child seat  130  is limited by a stop  158  which comes into abutment with the adjacent link  152 , as shown in  FIG. 12 . The result is that the foot end  160  of the child seat  130  abuts against the vehicle seat back  14  to limit clockwise angular movement about the anchorage units  16  and  18 .  
         [0036]      FIGS. 13 and 14  show a child seat  162  in which the relatively long links  152  are replaced by more compact L-shaped links  164  attached by pivot joints  166  to the foot end  160  of the child seat  162 , above the stop  158 . In the event of sudden deceleration, there is no significant change in the angle {acute over (α)}. Consequently, although the child seat  162  is more compact, the performance is not as good as that of the child seat  150  of FIGS.  10  to  12 . Nevertheless, there is an acceptable clearance a between the head of the dummy  140  and the reference surface  149 .  
         [0037]     In  FIGS. 15 and 16 , a child seat  170  has L-shaped links  172  attached to its releasable connectors  138 . However, each link  172  is connected to the child seat  170  by a first and second auxiliary links  174  and  176 . The first auxiliary link  174  has one end attached to the child seat  170  by a first pivot joint  178  and another end attached to the L-shaped link  172  by a second pivot joint  180 . The second auxiliary link  176  is longer than the link  174  and has one end attached to the child seat  170  by a third pivot joint  182  located below the first pivot joint and another end attached to the rigid link by a fourth pivot joint  184  located above the second pivot joint. The effect of this is that, in the event of sudden deceleration, the child seat turns in a clockwise direction so as to increase the angle {acute over (α)}. This results in an increased clearance a between the head of the dummy  140  and the reference surface  149 .  
         [0038]      FIGS. 17 and 18  show a child seat  186  having L-shaped links  172  attached to its releasable connectors  138 , as in  FIGS. 13 and 14 . In addition, a base rests on the seat cushion  12  and has side panels  188  pivotally attached to each side of the child seat  186  by respective pivot pins  189 . Each side panel carries a first pulley  192  below, and a second pulley  194  above, the pivot joint  166  attaching the corresponding L-shaped link  172  to the child seat  186 . A flexible cable  196  extends from a point  198  on the L-shaped link  172  at the junction between its two limbs, round the first pulley  192 , then round the second pulley  194 , to a point  200  on the corresponding side wing  202  of the seat  186 . In the event of an accident, the downward movement of the L-shaped link  172  causes the cable  196  to pull the upper part of the child seat  186  rearwardly, thus increasing the clearance a between the head of the dummy  140  and the reference surface  149 .  
         [0039]      FIGS. 19 and 20  show a modified version of the child seat  150  illustrated in  FIGS. 10 and 11 , corresponding parts being denoted by the same reference numerals. The long links  152  are replaced by cables  210  which extend from the releasable connectors  138 , through respective slots formed in guide members  212  mounted on the lower parts of the side wings  156 , to attachment points  214  on the upper parts of the side wings  156 . Operation is as described above with reference to  FIGS. 10 and 11 , the guide members  212  serving to limit the range of clockwise movement of the seat  150  during rebound.  
         [0040]     The invention is applicable to seats for use in aircraft as well as to seats for use in land vehicles.