WO2011112123A1

WO2011112123A1 - A backrest support mechanism

Info

Publication number: WO2011112123A1
Application number: PCT/SE2010/050253
Authority: WO
Inventors: Peter Axelsson; Clas Wergeland
Original assignee: Autoliv Development Ab
Priority date: 2010-03-08
Filing date: 2010-03-08
Publication date: 2011-09-15

Abstract

There is disclosed a backrest support mechanism for a motor vehicle seat, the mechanism comprising a squab-part (18/18a, 50, 57, 59, 78) configured for connection to the squab (63) of the seat, and a backrest-part (7, 7a) configured for connection to the backrest (2) of the seat. The parts are coupled to one another by a linkage arrangement (25, 30) configured to permit relative movement between the-squab part and the backrest-part. The squab-part comprises a guide element (59) which is fixed relative to the squab (63), and the back-rest part comprises a guide aperture (12,12a), the guide element (59) and the guide aperture (12,12a) being configured for cooperation in a manner effective to i) guide said relative movement in such a way that the backrest (2) reclines relative to the squab (63), and/or ii) define a predetermined end point to said relative movement.

Description

A BACKREST SUPPORT MECHANISM

The present invention relates to a backrest support mechanism, and more particularly relates to a backrest support mechanism for supporting the backrest of a seat intended to be mounted in a motor vehicle. A preferred backrest support mechanism in accordance with the invention may incorporate a recliner mechanism.

In order to accommodate occupants of various different shapes and sizes with individual comfort preferences, a seat for use in a motor vehicle may be provided with a recliner mechanism which connects the backrest and squab of the seat (or a frame of the backrest and/or squab). The recliner mechanism allows the backrest to be set at a preferred angle relative to the squab. The angle may be selected by the occupant of the seat, usually through the rotation of a control knob provided at the base of the backrest.

When a vehicle provided with a conventional seat is involved in a rear impact, the seat may be accelerated with a substantial forwards acceleration because the seat is secured to the floor of the vehicle. The occupant's posterior and torso will consequently be accelerated because of their intimate contact with the seat. The head of the occupant, however, is generally not in direct contact with the seat, and so due to its inertia will tend to remain stationary during an initial stage of the impact. Because the occupant's posterior and torso are being accelerated forwardly, this means that effectively the occupant's head may move rearwardly relative to the torso, thus bending the neck of the occupant. This can cause a so- called "whiplash" injury to the occupant.

It has been found that the risk of injury in a rear impact accident can be reduced if the seat is configured in such a way that the occupant's head couples quickly with the top part (e.g. the head restraint) of the backrest so as to prevent significant unsupported relative movement between the head and the backrest, and also in such a way that the backrest can

subsequently "yield", at least to a predetermined extent. In this way, the torso of the occupant can be caused to accelerate in a more gradual manner, and the head of the occupant can be supported thus reducing the risk of whiplash injury.

It is therefore desirable to provide a backrest support arrangement which is configured to permit the backrest of the seat to "yield" as proposed above in an energy-absorbing manner so as to gradually slow the relative movement of the occupant's torso, and which also define a clear stop point to the yielding movement. However, it is also desirable to ensure that such mechanisms are robust, space efficient, low in weight and inexpensive. Many previously proposed examples do not satisfy these objections, and indeed many are relatively complicated and bulky.

It is an object of the present invention to provide an improved backrest support mechanism for a motor vehicle seat.

According to the present invention, there is provided: a backrest support mechanism for a motor vehicle seat, the mechanism comprising a squab-part configured for connection to the squab of the seat, and a backrest-part configured for connection to the backrest of the seat, said parts being coupled to one another by a linkage arrangement configured to permit relative movement between the-squab part and the backrest-part, wherein the squab-part comprises a guide element which is fixed relative to the squab, and the back-rest part comprises a guide aperture, the guide element and the guide aperture being configured for cooperation in a manner effective to i) guide said relative movement in such a way that the backrest reclines relative to the squab, and/or ii) define a predetermined end point to said relative movement.

Preferably, the guide aperture defines a guide edge against which the guide element bears during said relative movement.

Advantageously, the guide element extends through the guide aperture as a loose fit within the aperture. Conveniently, the linkage arrangement comprises a deformable coupling member coupled to the squab-part and to the backrest part, the coupling member being arranged to resist said relative movement and configured to deform when subjected to a force in excess of a predetermined threshold and thereby permit said relative movement.

Preferably, the mechanism comprises a substantially pivotal coupling between the squab- part and the backrest-part, the coupling being configured such that said relative movement comprises a component of substantially pivotal movement between the squab-part and the backrest-part.

Advantageously, said pivotal coupling comprises a pivot-link which forms part of the linkage arrangement and which is pivotally connected to the squab-part and pivotally connected to the backrest-part. Conveniently, the mechanism comprises a releasable connection between said squab-part and said backrest-part, the connection being effective to prevent said pivotal movement and mechanism being configured such that said connection is released when the backrest is subjected to a rearward force. Preferably, said releasable connection is provided by a hook or recess formed on the backrest-part, the hook or recess engaging a cooperating region of the squab-part.

Advantageously, the mechanism further comprises a biasing member coupled to the backrest-part and to the squab-part and configured to bias the squab-part and the backrest- part towards one another such that said connection is released against the bias when the backrest is subjected to a rearward force in excess of a predetermined threshold.

Conveniently, said biasing member is coupled to said squab-part by engagement with said guide element.

Preferably, the mechanism further comprises a blocking member mounted to the squab-part for movement relative to the squab-part, the blocking member being moveable from an initial position in which it does not impede said relative movement between the squab-part and the backrest-part, to a blocking position in which it at impedes or limits said relative movement between the squab-part and the backrest-part.

Advantageously, said blocking member is arranged so as to substantially prevent said pivotal movement between the squab-part and the backrest-part. Conveniently, said blocking member is configured to be moved from said initial position to said blocking position by inertia.

Preferably, the blocking member is biased towards said initial position by a biasing force provided by a biasing arrangement, and is moveable to said blocking position if the force arising from its inertia exceeds the biasing force. Advantageously, the biasing arrangement comprises a biasing spring.

Conveniently, said biasing arrangement includes an over-dead-centre mechanism configured such that during movement of the blocking member from its initial position towards its blocking position, the action of the biasing force changes from biasing the blocking member towards its initial position to biasing the blocking member towards its blocking position. Preferably, at least part of the blocking member is arranged to cooperate with said guide aperture so as to engage a peripheral edge of the aperture when in said blocking position.

Advantageously, the blocking member is pivotally mounted to the squab-part for pivotal movement.

Conveniently, the mechanism is provided in combination with a motor vehicle seat.

According to another aspect of the present invention, there is provided a motor vehicle seat incorporating a mechanism of the type defined above.

So that the invention may be more readily understood, and so that further features thereof may be appreciated, embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 shows a backrest bracket for use in an embodiment of the present invention; Figure 2 shows a support plate for use in an embodiment of the present invention; Figure 3 shows a side plate for use in an embodiment of the present invention; Figure 4 shows the side plate of Figure 3, viewed from above;

Figure 5 shows a deformable coupling member for use in an embodiment of the present invention;

Figure 6 shows a pivot link for use in an embodiment of the present invention;

Figure 7 shows a biasing member for use in an embodiment of the present invention;

Figure 8 is an exploded view of a backrest support mechanism in accordance with an embodiment of the present invention incorporating the components illustrated in Figures 1 to 7;

Figure 9 is a perspective view of the support mechanism shown in Figure 8;

Figure 10 is a side elevational view of the support mechanism shown in Figures 8 and 9, showing the mechanism in an initial condition; Figure 1 1 is a view corresponding generally to that of Figure 10, but showing the mechanism with the side plate of Figures 3 and 4 removed;

Figure 12 is a view corresponding generally to that of Figure 1 1 , but showing the mechanism with the deformable coupling member of Figure 5 and the biasing member of Figure 7 removed;

Figure 13 is a view similar to that of Figure 1 1 , but shows the mechanism in an alternate condition;

Figure 14 is a view similar to that of Figure 12, but shows the mechanism in the alternate condition illustrated in Figure 13;

Figure 15 is a view similar to that of Figure 13, but shows the mechanism in a further alternate condition;

Figure 16 is a view similar to that of Figure 14, but shows the mechanism in the further alternate condition illustrated in Figure 15;

Figure 17 shows an alternative configuration of support plate for use in a second

embodiment of the present invention;

Figure 18 shows an alternative form of side plate for use in the second embodiment of the invention;

Figure 19 shows a blocking element for use in the second embodiment of the invention;

Figure 20 shows a connection element for use in the second embodiment of the invention;

Figure 21 is an exploded view of a backrest support mechanism in accordance with the second embodiment of the present invention, incorporating the components illustrated in Figures 1 , 5, 6, 7 and 17 to 20;

Figure 22 is a side elevational view of the support mechanism shown in Figure 21 , showing the mechanism in an initial condition;

Figure 23 is a view corresponding generally to that of Figure 22, but showing the side plate of Figure 18 removed; Figure 24 is a view corresponding generally to that of Figure 23, but showing the mechanism with the deformable coupling member of Figure 5, the biasing member of Figure 7, the connection element of Figure 20, and a spring all removed;

Figure 25 is a view similar to that of Figure 23, but shows the mechanism in an alternate condition;

Figure 26 is a view similar to that of Figure 24, but shows the mechanism in the alternate condition illustrated in Figure 25;

Figure 27 is a view similar to that of Figure 25, but shows the mechanism in a further alternate condition; and Figure 28 is a view similar to that of Figure 26, but shows the mechanism in the further alternate condition illustrated in Figure 27.

Referring now in more detail to figure 1 , there is illustrated a backrest bracket 1 for use in the mechanism of the present invention. The bracket preferably takes the form of a flat metal plate and is used to support the lower region of the backrest 2 of a vehicle seat. The bracket 1 will typically be connected to the backrest 2, or to a frame of the backrest 2, via a recliner (not shown) so as to allow the backrest to be set at a preferred angle relative to the squab of the seat. The recliner may be manually operated in order to adjust the angle between the backrest and bracket 1 , and hence adjust the angle between the backrest and the squab of the seat in a generally conventional manner. The backrest bracket 1 includes two outwardly extending connection lobes 3, 4, each of which is provided with a respective mounting aperture 5, 6. In the particular arrangement illustrated, the forwardly extending lobe 3 has a mounting aperture 5 which is slightly larger than the aperture 6 of the downwardly extending lobe 4.

Figure 2 illustrates a support plate 7, which also preferably takes the form of a flat metal plate. The support plate has a pair of connection lobes 8, 9 which are configured for connection to the lobes 3, 4 of the backrest bracket 1 , although it is to be appreciated that in alternative arrangements the support plate 7 can be formed integrally with the backrest bracket 1 as a single component. As will be noted, the connection lobes 8, 9 of the support plate are also provided with respective mounting apertures 10, 1 1 . The mounting aperture 10 of the upwardly directed lobe 8 has a size corresponding generally to that of the mounting aperture 5 of the support plate, and the mounting aperture 1 1 of the rearwardly directed lobe 9 has a size corresponding generally to that of the mounting aperture 6 of the support plate.

The support plate 7 has a guide aperture 12 formed through its central region. The guide aperture has a generally triangular form and defines a substantially straight rear guide edge 13 which extends generally downwardly and forwardly from the rear connection lobe 9. The lowermost front corner of the triangular aperture defines a somewhat elongated recess 14 of arcuate form.

The forward region 15 of the support plate 7 is configured so as to define an arcuate recess 16, and a substantially linear guide edge 17 immediately below the recess 16. Turning now to consider figures 3 and 4, there is illustrated a side plate 18. The side plate is preferably formed from sheet metal and is generally elongate. A respective mounting tab 19, 20 is provided at each end of the side plate, the two tabs being substantially co-planar. Each mounting tab is provided with a respective mounting aperture 21 , 22. As will be noted, the mounting tabs 19, 20 are interconnected by a tapered central region 23 of the plate, the central region being generally planar but offset slightly from the plane of the tabs (as illustrated most clearly in figure 4). The central region 23 has a relatively small aperture 24 formed therethrough.

A coupling member 25 is shown in figure 5. The coupling member is preferably formed as a metal plate and is specifically configured so as to have a deformable body. More particularly, it will be noted that the coupling member 25 has a generally C-shaped body with a first end 26 and a second end 27. Respective connection apertures 28, 29 are provided through the first and second ends 26, 27 of the coupling member 25.

A pivot link 30 is shown in figure 6. The pivot link 30 comprises an elongate body with a first end 31 and a second end 32, each end having a respective aperture 33, 34. A biasing member is 35 is shown in figure 7. The biasing member has a mounting aperture 36 formed through a ring 37. An elongate arm 38 extends generally radially outwardly from the ring 37, the arm being generally arcuate or bent. A small recess 39 is defined at the free end 40 of the arm 38.

Turning now to consider figure 8, the assembly of the mechanism will now be described. Firstly, it is to be appreciated that the support plate 7 is substantially rigidly connected to the backrest bracket 1 . More particularly, the upper lobe 8 of the support plate 7 is connected to the forward lobe 3 of the backrest plate 1 via a first bolt 41 which extends through the aligned apertures 5, 10 of the two lobes, from the side of the backrest bracket. Similarly, the rear lobe 9 of the support plate 7 is connected to the lower lobe 4 of the backrest bracket 1 via a second bolt 42 which extends though the aligned apertures 6, 1 1 . However, it will be noted that in contrast to the first bolt 41 , the second bolt 42 extends through the apertures 6, 1 1 from the side of the support plate 7. As will be immediately evident from figure 8, the two bolts 41 , 42 also serve to connect and mount other components of the mechanism, as will be explained. Considering initially the first bolt 41 , it will be seen that this bolt is also effective to mount the first end 26 of the coupling member 25 to the mechanism. More particularly, an annular bearing 43 is provided, the bearing having an outer diameter sized to form an interference or close-sliding fit within the upper aperture 28 of the connection member 25. The inner diameter of the bearing 43 is configured to receive the shank 44 of the first bolt 41 as an interference or close-sliding fit. The bearing 28 is thus inserted into the upper aperture of the coupling member 25, such that the bearing lies substantially flush with the coupling member. The bearing 43 is then slid over the shank 44 of the first bolt 41 , whereupon a cooperating flanged nut 45 is threadedly engaged with the end of the shank 44 in order to interconnect the coupling member 25, the upper lobe 8 of the support plate 7 and the forward lobe 3 of the backrest bracket 1. It is to be appreciated that by virtue of the bearing 43, the upper end 26 of the coupling member 25 is pivotally connected to the support plate 7.

Turning now to consider the second bolt 42, it will be seen that this bolt is effective also to mount the first end 31 of the pivot link 30 and the ring part 37 of the biasing member 35. More particularly, an annular flanged bush 46 is provided which is sized for receipt within the aperture 36 of the biasing member 35. The bush 46 has an inner diameter which is substantially equal to the diameter of the upper aperture 33 of the pivot link 30. The bolt 42 has a stepped shank 47 having a first section 48 sized for receipt through the bush 46 and the aperture 33 for rotation relative to both. A narrower second section 49 of the shank is sized for receipt through the co-aligned apertures 6, 1 1 of the backrest bracket 1 and the support plate 7. As will therefore be noted, the bolt 42 serves to interconnect the biasing member 35, the upper end 31 of the pivot link 30, the rear lobe 9 of the support plate 1 and the lower lobe 4 of the backrest plate 1 . The pivot link 30 and the biasing member 35 are both mounted for pivotal movement relative to the support plate 7, about an axis defined by the bolt 42.

Turning now to consider the side plate 18, it will be noted that the forward mounting tab 19 is pivotally connected to the second end 27 of the coupling member 25 via a first mounting 5 bush 50. The mounting bush 50 has a stepped shank 51 , through which there is defined a central bore 52. The stepped shank 51 has a first large diameter region 53 which is sized to fit within the recess 16 provided along the front edge of the support plate 1 . A central, medium sized region 54 of the shank is sized for receipt within an annular flanged bush 55 which is pressed into the lower aperture 29 of the coupling member 25. Finally, a terminal i o end region 56 of the shank is sized to engage the mounting aperture 21 formed through the forward tab 19 of the side plate 18 as a tight interference fit.

The rear mounting tab 20 of the side plate is pivotally connected to the second end 32 of the pivot link 30 in a generally identical way, and via a generally identical second mounting bush 57, together with another annular flanged bush 58 which is received within the lower aperture 15 34 of the pivot link 30.

The mechanism additionally includes a guide element, which in the illustrated embodiment takes the form of a guide post 59. The guide post 59 illustrated is of a two-part construction. A first part of the post 59 has a hollow cylindrical shank 60 which terminates at one end with an enlarged head 61 . The second part of the guide post comprises a smaller shank and

20 head 62, the smaller shank being engaged (for example threadedly) within the larger hollow shank 60. The guide post 59 is fixed to the side plate 18 such that the smaller shank of the second part is received through the small aperture 24 formed through the central region of the side plate. The guide post is thus mounted so as to extend from the side plate 18 and through the guide aperture 12 of the support plate 7. Additionally, it is to be appreciated that

25 the arcuate arm 38 of the biasing member 35 extends around the guide post such that the guide post 59 is received within the small recess 39 at the free end 40 of the arm.

The assembled support mechanism thus has the initial configuration illustrated in figures 9 and 10.

The mechanism is connected to the squab 63 (frame or bracket thereof) in the manner

30 illustrated schematically in figure 10. More particularly, the mechanism is connected to the squab 63 via a pair of fixing bolts (not shown) which pass through the central bores 52 of the front and rear mounting bushes 50, 57. As will thus be appreciated, this connection to the squab 63 is effective to retain the side plate 18, the associated guide post 59, and the two mounting bushes 50, 57 in fixed positions relative to the squab 63 of the seat. These components thus cooperate to define a fixed squab-part of the mechanism. Similarly, it is to be remembered that the support plate 7 is fixedly secured to the backrest bracket 1 by the two bolts 41 , 42, and so can be considered to represent a back-rest part of the mechanism.

Turning now to consider figures 1 1 to 16, operation of the above-described mechanism during a rear-impact accident will now be explained. It is to be noted that figures 1 1 to 16 all show a reference line 64, which represents a notional setting of the backrest angle relative to the squab of the seat.

Figures 1 1 and 12 both show the mechanism in an initial condition representative of the backrest being set at a preferred angle relative to the squab of the seat during normal use of the seat and vehicle. Figure 1 1 shows the mechanism with the side plate 18 removed for clarity, and figure 12 shows the mechanism with the coupling member 25 and the biasing member 35 also removed for further clarity. As will be noted from figure 12 in particular, in this initial condition the forward mounting bush 50 is fully engaged within the cooperating recess 16 provided along the front edge of the support plate 7. This engagement between the forward mounting bush 50 and the recess 16 forms a connection (which is releasable as will be explained in further detail below) between the support plate 7 and the bush 50 which is effective to prevent any rotational movement of the support plate about the axis 65 defined by the rear mounting bush 57.

It is also to be noted that in the initial condition illustrated in figures 1 1 and 12, the main shank 60 of the guide post 59 bears against the guide edge 13 of the guide aperture 12, and is located approximately half-way along the guide edge 13. Having regard to figure 1 1 , the resilient nature of the arm 38 of the biasing member 35 is effective to apply a biasing force between the second bolt 42 (which is fixed relative to the support plate 7 and the backrest bracket 1 ) and the guide post 59 (which is fixed relative to the side plate 18 and hence also the squab 63 of the seat). The biasing member 35 thus serves to bias the support plate 7 towards the forward mounting bush 50, such that the recess 16 remains engaged with the mounting bush 50.

In the event of a rear impact, the posterior and torso of the seat occupant are pressed against the lower portion of the backrest 2 as the vehicle in which the seat is mounted is moved forwards by the impact. This force of the occupant's posterior and torso is illustrated schematically by arrow 66 in figures 13 and 14. If the force is above a predetermined threshold defined by the resilience of the biasing member 35, it will overcome the biasing force applied by the biasing member 35 and thus urge the backrest 2 rearwardly and cause rearward movement of the backrest bracket 1 and the support plate 7 relative to the components of the mechanism (most notably the guide post 59) which are fixed relative to the squab.

As the support plate 7 is urged rearwardly in this way, the pivot link 30 is caused to rotate (clockwise as illustrated) around the rear mounting bush 57. Also, it will be noted that the guide aperture 12 is thus moved relative to the fixed guide post 59, this movement being effective to bring the guide post 59 closer to the front end of the guide edge 13. As will be appreciated, this movement thus occurs against the biasing force of the biasing member 35, the arm 38 of the biasing member effectively being deformed as illustrated in figure 13. However, because the guide post 59 bears against the guide edge 13 of the aperture 12, and also because the forward mounting bush 50 is initially fully engaged within the recess 16, pivotal movement of the support plate 7 is limited, and indeed is preferably substantially prevented, such that the support plate 7 moves rearwardly relative to the fixed guide post 59 and the two mounting bushes in a substantially translational rather than rotational manner.

The above-mentioned relative movement between the support plate 7 and the components fixed relative the squab is short, and preferably ceases when the rear edge of the support plate 7 contacts the rear mounting bush 57. As this short-range movement also occurs against the bias of the biasing member 35, it is controlled in such a manner that the torso of the seat occupant will move into the backrest 2 of the seat, thus becoming securely embedded in the upholstery of the backrest. This also causes the occupant's head to couple promptly with the headrest provided at the top of the backrest.

In the embodiment illustrated in the drawings, the deformable coupling member 25 is also caused to deform slightly during the above-mentioned initial movement of the backrest. This deformation thus further contributes to the above-mentioned control of the movement.

However, in alternative embodiments it is envisaged that the connection of either or both ends 26, 27 of the coupling member 25 may be configured so as to include a degree of "slack" which would thus allow the initial movement of the support plate 7 to occur without deformation of the coupling member 25, the movement occurring only against the biasing force provided by the biasing member 35.

As illustrated most clearly in figure 14, the effect of this initial rearwards movement of the support plate 7 relative to the components fixed to the squab of the seat, is that the recess 16 is moved out of engagement with the forward mounting bush 50. The connection between these components is thus released. Upon release of this connection, the movement of the support plate 7 relative to the fixed components of the mechanism is no longer restricted by the forward mounting bush 50. The support plate 7 thus becomes free for subsequent further movement in a substantially pivotal manner, as will now be described in further detail with reference to figures 15 and 16.

As will be see from figures 15 and 16, once the connection between the forward mounting bush 50 and the recess 16 is released as described above, the support plate 7 is allowed to move more freely, and with a generally pivotal action about the axis 65 defined by the rear mounting bush 57. More particularly, it will be seen that the pivot link 30 rotates about the axis 65. The actual movement of the support plate 7 continues to be guided by the cooperation between the fixed guide post 59 and the guide edge 13 of the aperture 12, the guide post effectively moving along the guide edge 13 towards the recess 14 at the front of the aperture 12.

As the support plate 7 moves in this manner, the backrest 2 is thus caused to recline as indicated by the movement of the reference line 64. As will be noted from figure 15, this reclining movement causes deformation (and in particular elongation) of the deformable coupling member 25. This deformation of the coupling member absorbs energy and thus serves to reduce the risk of injury to the seat occupant by controlling the deceleration of the occupant's torso. The above-mentioned energy-absorbing movement of the support plate 7 relative to the fixed components of the mechanism has a limited range in order to prevent the backrest becoming excessively reclined relative to the squab. More particularly, the mechanism is configured to define a predetermined end point to the movement. The end point is defined by engagement of the guide post 59 within the recess 14 at the front of the aperture which prevents further relative movement between the support plate 7 and the guide post 59. Turning now to consider figures 17 to 28, a mechanism in accordance with another embodiment of the invention will now be described. The arrangement of figures 17 to 28 is in many ways substantially identical to the arrangement of figures 1 to 16, and indeed shares many of the components of the arrangement of figures 1 to 16. Such components will not be 5 described in detail again, and are identified by the same reference numerals in figures 17 to 28 for convenience and clarity.

Figure 17 illustrates a modified form of support plate 7a which forms part of the alternative arrangement. As will be noted, the overall shape and configuration of the support plate 7a is identical to that of the support plate 7 of the arrangement of figure 1 to 16. The only

i o difference concerns the central guide aperture 12a, which in this arrangement is somewhat larger and no longer triangular in form. The guide aperture 12a of this arrangement is generally rhomboid in configuration, and retains a guide edge 13a which extends generally downwardly and forwardly from the rear connection lobe 9. The forward edge 67 of the aperture 12a has a small recess 68, and the rear edge 69 has a correspondingly shaped

15 projection 70.

Figure 18 illustrates a modified form or side plate 18a. The side plate 18a is generally identical to the side plate 18 of the arrangement illustrated in figures 1 to 16. The only difference is that the modified side plate 18a has a small finger 71 which extends forwardly and downwardly from the rear mounting tab 20. The finger 71 terminates with a small end 20 tab 72 through which is formed an aperture 73.

Figure 19 illustrates a blocking member 74. The blocking member can also be seen, in perspective view, in figure 21. The blocking member 74 is of generally "tear-drop" shape, and comprises a planar element 75 which is preferably formed of metal and which has significant mass. Secured to the top end of the planar element 75 (or alternatively formed integrally

25 therewith), is a smaller planar element 76. The smaller element 76 defines a forwardly

directed projection 77 and has a substantially circular body part 78. As illustrated most clearly in figure 21 , the smaller planar element 76 lies in a plane which is offset to the side of the larger planar element 75. A small upwardly directed tab 79 is provided, the tab having an outwardly directed spigot 80. A mounting aperture 81 is formed through the top region of the

30 blocking member, passing through both of the planar elements 75, 76 and centred with

respect to the circular body part 78. Figure 20 illustrates a resilient link arm 82, which is preferably formed from a length of resilient wire. The link arm 82 has a C-shaped form and has a small fixing loop 83 formed at each end.

Turning now to consider figure 21 , the assembly of the mechanism will now be described. However, it will be immediately evident that in many respects the modified mechanism of this embodiment is assembled in exactly the same manner as the mechanism described above in connection with figures 1 to 16. Only the features of the modified mechanism which are different will thus be described in detail.

In the modified arrangement of figure 21 , the guide post 59 is inserted through the mounting aperture 81 of the blocking element, and also through a cylindrical guide collar 84. The collar 84 will thus extend between the smaller element 76 of the blocking member 75 and the side plate 18a, and will be received in the recess 39 of the biasing member 35 (shown most clearly in figure 23. The upper fixing loop 83 of the link arm 82 is hooked over the spigot 81 , and the lower fixing loop 83 is connected to one end of a helically wound compression spring 85. The other end of the compression spring is connected to the tab 72 (via its aperture 73) carried by the side plate 18a. The link arm 82 extends around the front side of the collar 84.

As will thus be appreciated, the blocking element 74 is affixed to the guide post 59 in a pivotal manner. The large planar element 75 of the blocking element lies to the side of the support plate 7a, but the small planar element 76 actually lies within the guide aperture 12a and is thus coplanar with the support plate 7a.

The assembled mechanism thus has the configuration illustrated in figure 22 and will be affixed to the squab 63 of the seat and the backrest 2 of the seat in an identical manner to that described above in connection with the arrangement of figures 1 to 16.

Before moving on to consider the way in which the mechanism of this embodiment operates in a rear impact accident, it is relevant to note the precise arrangement of the link arm 82 and the spring 85, which is shown most clearly in figure 23 (the side plate 18a being removed for clarity). As will be appreciated, the spring 85 is normally held in tension, acting between the lower end of the link arm 82 and the mounting tab 72 of the side plate 18a. In the initial condition of the mechanism illustrated in figure 23, the spring 85 thus applies a biasing force to the link arm 82, the force acting along the line 86 shown in figure 23. As will be appreciated, the force line 86 passes through both ends of the link arm 82, but importantly passes just to the rear of the central axis 87 of the guide post 59 and its associated collar 84.

Figure 24 shows the mechanism in the same initial configuration illustrated in figure 23, but with the coupling member 25, the biasing member 35, the link arm 82 and the spring 85 all removed so that the initial position of the blocking member 74 and the guide collar 84 can be seen more clearly. In this configuration, the blocking member 74 hangs generally vertically under its own weight in the manner of a pendulum, and its upwardly directed tab 79 is located generally adjacent the projection 70 formed along the rear edge of the guide aperture 12a. As will also be noted, the projection 77 of the blocking member is located generally centrally within the guide aperture 12a. During normal driving conditions the biasing force of the spring 86 is effective to retain the blocking member 74 in this initial condition.

Upon impact from the rear, the posterior and torso of the seat occupant are again pressed against the lower portion of the backrest 2 as the vehicle in which the seat is mounted is moved forwards by the impact. This force of the occupant's posterior and torso is illustrated schematically by arrow 66 in figures 25 and 26. If the force is above a predetermined threshold defined by the resilience of the biasing member 35, it will overcome the biasing force applied by the biasing member 35 and thus urge the backrest 2 rearwardly and cause rearward movement of the backrest bracket 1 and the support plate 7a relative to the components of the mechanism which are fixed relative to the squab, in a generally identical manner as described above in connection with the arrangement of figures 1 to 16. However, the blocking member 74 and its associated component parts perform an additional function in the arrangement of figures 17 to 28.

As will be appreciated, during a rear impact, the side plate 18a and the various component parts which are fixed to it (most notably the guide post 59 extending through the blocking member 74) will be accelerated forwardly by the force of the impact. However, the blocking element 74 has inertia due to its weight, which means that if the side plate 18a and the guide post 59 are accelerated forwardly, a force is effectively exerted on the blocking member 74 in a rearward direction relative to the side plate 18a. In the event that a severe rear impact occurs, the force exerted on the blocking member 74 in this manner will be large and will be in excess of the biasing force exerted on the blocking member 74 by the spring 85. In this situation the force of the spring 85 is thus overcome, and the blocking member rotates about the guide post 59 in a rearward direction as illustrated in figures 25 and 26. The tab 79 at the top of the blocking member 74 to which the biasing spring 85 is attached is thus caused to rotate forwardly of the axis 87 about which the blocking member 74 is rotating. As illustrated in figure 25, this causes the line of action 86 along which the biasing force acts to move forwardly of the axis 87 about which the blocking member 74 rotates. The action of the biasing force from the spring 85 thus changes from biasing the blocking member in a clockwise sense (as illustrated) towards its initial position, to biasing the blocking member in the opposite, (counter-clockwise as illustrated) sense. The link arm 82, the tab 79 and the spring 85 thus form part of a so-called over-dead-centre mechanism.

The blocking member 74 is thus caused to rotate as described above, and this rotation is effective to quickly lower the projection 77. The projection 77 is thus moved into

engagement with the recess 68 at the front of the guide aperture 12a as the support plate 7a begins its rearward movement in an otherwise substantially identical manner to that described above in connection with the embodiment of figures 1 to 16. However, the engagement of the projection 77 with the recess 68 prevents further relative movement between the support plate 7a and the fixed mounting lugs 50, 57. Thus, in the event of a severe rear impact, further rearward tilting of the backrest is minimised.

Conversely, in a low or average severity rear impact, the side plate 18a and the various component parts which are fixed to it (most notably the guide post 59 extending through the blocking member 74) will not be accelerated forwardly as quickly, and thus the relative force on the blocking member 74 will be low. In such a situation, the low force on the blocking member 74 will be insufficient to overcome the biasing force 86 on the blocking member 74 which is exerted by the spring 85. The blocking member 74 will thus be retained in its normal position relative to the side plate 18a as illustrated generally in figures 23 and 24 as the force 66 exerted on the backrest by the seat occupant's posterior and torso begins to move the support plate 7a. The blocking movement of the blocking member 74 illustrated in figures 25 and 26 will thus not occur, leaving the support plate 7a free to continue its pivotal movement, guided by cooperation between the circular body part 78 of the blocking member and the rear guide edge 13a of the guide aperture 12a, as illustrated in figures 27 and 28. However, it is to be appreciated that as the support plate 7a nears the end of its limited range of movement, as defined by engagement of the circular body part 78 with the front corner of the guide aperture 7a (figure 28), the blocking member 74 is caused to rotate clockwise (as illustrated) as the projection 77 impinges on the front edge 67 of the aperture 12a, above the recess 68. As will be appreciated, the modified arrangement of figures 17 to 28 thus operates in a generally similar manner to the arrangement of figures 1 to 16 in the event of a low or average severity rear impact, but operates in a different manner in the event of a severe rear impact, such that the backrest 2 of the seat is prevented from reclining (at least to any significant degree) relative to the squab.

It is to be appreciated that whilst the invention has been described in detail above with reference to two specific embodiments, various modifications or alterations may be made to the mechanism without departing from the scope of the invention. For example, whilst the two embodiments above both comprise a support plate 7, 7a which is separate from but fixed to the backrest bracket 1 , it is envisaged that in alternative arrangements the support plate 7, 7a may be formed integrally with the backrest bracket or other supporting structure of the backrest 2.

Also, whilst the invention has been described with reference to embodiments using bolts to interconnect certain components, it is envisaged that alternative arrangements could use rivets or other convenient fixing elements.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or integers.

The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

Claims

1 . A backrest support mechanism for a motor vehicle seat, the mechanism comprising a squab-part (18/18a, 50, 57, 59, 78) configured for connection to the squab (63) of the seat, and a backrest-part (7, 7a) configured for connection to the backrest (2) of the seat, said parts being coupled to one another by a linkage arrangement (25, 30) configured to permit relative movement between the-squab part and the backrest-part, the mechanism being characterised in that the squab-part comprises a guide element (59) which is fixed relative to the squab (63), and the back-rest part comprises a guide aperture (12,12a), the guide element (59) and the guide aperture (12,12a) being configured for cooperation in a manner effective to i) guide said relative movement in such a way that the backrest (2) reclines relative to the squab (63), and/or ii) define a predetermined end point to said relative movement.

2. A mechanism according to claim 1 , wherein the guide aperture (12,12a) defines a guide edge (13,13a) against which the guide element (59, 78) bears during said relative movement.

3. A mechanism according to claim 1 or claim 2, wherein the guide element (59, 78) extends through the guide aperture (12, 12a) as a loose fit within the aperture.

4. A mechanism according to any preceding claim, wherein the linkage arrangement comprises a deformable coupling member (25) coupled to the squab-part (50) and to the backrest part (7, 7a) the coupling member (25) being arranged to resist said relative movement and configured to deform when subjected to a force in excess of a predetermined threshold and thereby permit said relative movement.

5. A mechanism according to any preceding claim, comprising a substantially pivotal coupling (30, 42, 57) between the squab-part and the backrest-part, the coupling being configured such that said relative movement comprises a component of substantially pivotal movement between the squab-part and the backrest-part.

6. A mechanism according to claim 5, wherein said pivotal coupling comprises a pivot- link (30) which forms part of the linkage arrangement and which is pivotally connected to the squab-part (57) and pivotally connected to the backrest-part (7, 7a).

7. A mechanism according to claim 5 or claim 6, comprising a releasable connection (16, 50) between said squab-part and said backrest-part, the connection being effective to prevent said pivotal movement and mechanism being configured such that said connection is released when the backrest (2) is subjected to a rearward force.

8. A mechanism according to claim 7, wherein said releasable connection is provided by a hook or recess (16) formed on the backrest-part (7, 7a) , the hook or recess engaging a cooperating region (50) of the squab-part.

9. A mechanism according to claim 7 or claim 8, further comprising a biasing member (35) coupled to the backrest-part and to the squab-part and configured to bias the squab-part and the backrest-part towards one another such that said connection is released against the bias when the backrest (2) is subjected to a rearward force in excess of a predetermined threshold.

10. A mechanism according to claim 9, wherein said biasing member (35) is coupled to said squab-part by engagement with said guide element (59, 84).

1 1 . A mechanism according to any preceding claim, further comprising a blocking member (74) mounted to the squab-part (18a) for movement relative to the squab-part, the blocking member (74) being moveable from an initial position in which it does not impede said relative movement between the squab-part (18a) and the backrest-part (7a), to a blocking position in which it at impedes or limits said relative movement between the squab- part (18a) and the backrest-part (7a).

12. A mechanism according to claim 1 1 as dependent upon any one of claims 5 to 10, wherein said blocking member (74) is arranged so as to substantially prevent said pivotal movement between the squab-part and the backrest-part.

13. A mechanism according to claim 1 1 or claim 12, wherein said blocking member (74) is configured to be moved from said initial position to said blocking position by inertia.

14. A mechanism according to claim 13, wherein the blocking member is biased towards said initial position by a biasing force (86) provided by a biasing arrangement (82, 85), and is moveable to said blocking position if the force arising from its inertia exceeds the biasing force.

15. A mechanism according to claim 14, wherein the biasing arrangement comprises a biasing spring (85).

16. A mechanism according to claim 14 or claim 15, wherein said biasing arrangement includes an over-dead-centre mechanism (79, 82, 85) configured such that during movement of the blocking member (74) from its initial position towards its blocking position, the action of the biasing force (86) changes from biasing the blocking member (74) towards its initial position to biasing the blocking member (74) towards its blocking position.

17. A mechanism according to any one of claims 1 1 to 16, wherein at least part (76, 78) of the blocking member (74) is arranged to cooperate with said guide aperture (12a) so as to engage a peripheral edge (67, 68) of the aperture when in said blocking position.

18. A mechanism according to any one of claims 1 1 to 17, wherein the blocking member (74) is pivotally mounted to the squab-part (18a) for pivotal movement.

19. A mechanism according to any preceding claim provided in combination with a motor vehicle seat (2, 63).

20. A backrest support mechanism for a motor vehicle seat substantially as hereinbefore described with reference to and as shown in figures 1 to 16 of the accompanying drawings.

21 . A backrest support mechanism for a motor vehicle seat substantially as hereinbefore described with reference to and as shown in figures 17 to 26 of the accompanying drawings.