EP2038140A2

EP2038140A2 - Seat

Info

Publication number: EP2038140A2
Application number: EP07733377A
Authority: EP
Inventors: Steven Cousins; Christopher Owen
Original assignee: Cranfield University
Current assignee: Cranfield University
Priority date: 2006-06-27
Filing date: 2007-06-26
Publication date: 2009-03-25
Also published as: WO2008001071A3; WO2008001071A2; GB0612662D0

Abstract

A seat (10) for supporting an occupant in the event of a significant force (F) being applied to the seat in the same, first, direction (A) as the occupant is facing comprises a seat back (12) rotatable substantially about a first axis (16) lying substantially transverse to the first direction and higher than the H-point reference (H) of the seat, and control (20) means for allowing controlled rotation of the seat back about said axis in the event of said significant force being applied.

Description

TITLE : SEAT

DESCRIPTION

TECHNICAL FIELD The present invention relates to seats for supporting an occupant and particularly, but not exclusively, to seats for use in vehicles.

BACKGROUND ART Over the decades, seating manufacturers have been dramatically reducing the weight of vehicle _,. seat structures in order to lower the overall vehicle mass and improve fuel efficiency. However, problems concerning the structural integrity of such vehicle seating have been highlighted as far back as 1989 when, in America, numerous vehicle manufacturers were forced to face legal proceedings due to injuries and fatalities experienced by consumers when seats collapsed in an uncontrolled manner during relatively low speed rear impacts. Whilst the risk of occupant injuries associated with such a failure can be decreased if the seatback is considerably strengthened, such strengthening may increase the likelihood of rear impact induced whiplash trauma such as neck pains, headaches, blurred vision, tinnitus, dizziness, concussion or numbness.

GB2284393 (Totani) discloses a car seat having a yielding seat back and deforming seat pan in a so-called

'catcher's mitt' arrangement. To accommodate the deforming seat pan, Totani requires a collapsing vehicle floor or a unoccupied volume such as a storage bin located under the seat. Apart from being impractical for retrofit applications, the lack of seating support as the seatback and pan drop away may cause further injury. The system of Totani may also be expensive, using as it does a central processing unit (CPU) , collision sensor and battery to deploy the system.

Other ^λcatcher's mitt' arrangements deploy by means of cheaper yielding locking mechanisms. However, these too lack any control of the deploying seating structures once the locking mechanism has yielded. Moreover, such yielding structures or seatback designs may not address the difference in seated occupant mass and may not deploy for lighter occupants. Other ^catcher's mitt' arrangements also do not address how the occupant is to be restrained after seatback/seat pan deployment: as the occupant is displaced into the seat, there is a change in the relationship between the occupant's reference points and the location of the restraint system's anchorage and belt runs. This could result in the occupant being unrestrained during any subsequent vehicle impacts, for example an impact with a vehicle in front following an initial shunt from behind.

The present invention has as an objective the mitigation of one or more of the above disadvantages.

DISCLOSURE OF INVENTION

According to a first aspect of the present invention, there is provided a: seat for supporting an occupant in the event of a significant force being applied to the seat in the same, first, direction as the occupant is facing; the seat comprising a seat back rotatable substantially about a first axis lying substantially transverse to the first direction and higher than the H-point reference of the seat ; the seat further comprising control means for allowing controlled rotation of the seat back about said axis in the event of said significant force being applied.

The H-point measurement is a datum or reference point used in the verification of seat construction and defined as the pivot centre of the torso and the thigh of the 3-D H-machine (Regulation 14, 2004 - Uniform Provisions Concerning the Approval of Vehicles with Regard to Safety- belt Anchorages, ISOFIX Anchorages Systems and ISOFIX Top Tether Anchorages. Legislation: ECE - United Nations - Revision 3, Amendment No. 3; also Regulation 16, 2005 - Uniform Provisions Concerning the Approval of Safety Belts, Restraint Systems, Child Restraint Systems and ISOFIX Child Restraint Systems for Occupants of Power Driven Vehicles. Legislation: ECE - United Nations Revision 5, Addendum 15) . It may also be referred to as the occupant design position, the Seating Reference Point (SRP) or the R-point.

Control of the rotation of the seat back in the event of a significant force being applied to the seat in the same direction as the occupant is facing, e.g. as in a collision with a vehicle coming from behind, facilitates control of the occupant's acceleration time history and seated position in order that injury might be reduced. Advantageously, the seat may also comprise a seat pan rotatable substantially about a second axis lying substantially parallel to the first axis and forward of the H-point of the seat when viewed in said first direction. Such an arrangement can provide the occupant with greater support.

The seat pan may be kinematically linked to the seat back so that movement of the seat back also results in motion of the seat back and, optionally, vice versa.

The control means may be means for absorbing energy transmitted by rotation of the seat back about the first axis .

The control means may be configured to resist rotation of the seat back about the first axis up to a threshold and, above said threshold, to absorb the energy of rotation of said seat back.

In preferred embodiments, the rotation of the seat back or seat pan about their respective axes takes place about a pivot.

The control means may be fixed between the seat pan or seat back and a point fixed relative to the vehicle.

The control means may have a rotational action. The control means may be mounted about a respective axis of rotation of the seat pan or seat back.

The control means may have a linear action. It may be mounted between the seat pan or seat back and a point fixed relative to the vehicle. This point may be on a frame for attachment to the vehicle and about which the seat pan and seat back can rotate.

The control means may comprise a spring. The elastic element of the spring may be a solid and/or a gas . The spring may be pre-loaded, either in tension or compression, and the seat may comprise means for adjusting the pre-loading. The seat may further comprise means restricting the seat back or seat pan to rotation in one direction only, thereby preventing the spring once loaded from unloading into the occupant. Such means may comprise locking devices, e.g. a ratchet, which may also be releasable.

The control means may comprise a damper, which may use gas as the damping fluid and which may also include a valve configured to prevent damping gas flow until such time as the significant force is applied, thereby allow the means to act as a gas spring in the meantime. The valve may be configured to be controlled by a sensor located remotely of the seat. The control means may comprise a plastically deformable element. The element may be configured to deform in compression and may have a honeycomb structure of the kind conventionally used in crash impact absorbing structures. Alternatively, the element may be configured to deform plastically in tension. Where the seat has a frame, the plastically deformable element may be incorporated into that frame.

According to a second aspect of the present invention, there is provided a: seat for protecting its occupant in the event of a significant force being applied to the seat in the same, first, direction as the occupant is facing; the seat comprising a seat back rotatable substantially about a first axis lying substantially transverse to the first direction and higher than the H-point of the seat; the seat further comprising an occupant seat belt anchor kinematically linked to the seat back and configured to move in the opposite direction to said first direction in the event of said significant force being applied.

Moving the occupant seat belt anchor against the force acting at the back of the occupant may reduce the likelihood of the occupant being injured by being pushed forward or sideways, as may happen if, after an initial rear impact, there is frontal or side impact as the shunted vehicle impacts one directly in front of it. Advantageously, the seat may also comprise a seat pan rotatable substantially about a second axis lying substantially parallel to the first axis and forward of the H-point of the seat when viewed in said first direction. Such an arrangement can provide the occupant with greater support.

The seat pan may be kinematically linked to the seat back so that movement of the seat back also results in motion of the seat back and vice versa.

The occupant seat belt may also be configured to move downwards in the event of said significant force being applied.

In both aspects of the invention, the first axis may lie behind the H-point of the seat when viewed in said first direction. Similarly, the second axis may lie below the H-point of the seat. The seat back may comprise a head restraint located higher than the first axis.

The seat may comprise means for controlling the position of one of the seat pan or seat back in dependence on the position of the other of the seat pan or seat back. The means may be a mechanical linkage system.

The seat may comprise support means configured to support the occupant in the region between the seat pan and the seat back in the event of said significant force being applied. The support means may be attached to the seat pan and/or the seat back. In particular, the support means may be slidably mounted within one of the seat pan and seat back and pivotally mounted to the other of the seat pan and seat back. The support means may be substantially planar and configured to support the occupant in a direction substantially perpendicular to the plane.

With regard to the second aspect of the invention, the occupant seat belt anchor may be attached to the support.

Moreover, the seat may comprise all of the anchor points of the seat belt, resulting in a restraint system that is fully integrated into the seat. Compared to arrangements in which an upper seat belt support is anchored to a B-pillar of a car, such an arrangement may result in a reduced amount of exposed seat belt webbing. This in turn may reduce the amount of belt elongation during an impact event. Moreover, the upper seat belt support or supports in such an integrated arrangement will typically be located more closely to the occupant's shoulders, with the result that the occupant experiences effective restraint earlier into the impact event. Similarly, in the event of any rotation of the seat frame under loading, effective restraint of the occupant will be maintained. This is in contrast to arrangements in which the upper seat belt support is attached to the B- pillar and where a gap may open between the occupant and the belt as the seat frame deforms.

BRIEF DESCRIPTION QF DRAWINGS

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figures IA and B are diagrammatic illustration of a seat according to a first aspect of the present invention;

Figures 2A and B show the envisaged occupant response resulting from the first aspect of the invention;

Figures 3A and B show an embodiment of the seat according to the present invention when set up for a light person;

Figures 4A and B show an embodiment of the seat according to the present invention when set up for a heavy person;

Figures 5A and B are detailed perspective views of a weight adjuster mechanism in low and high pre-tension positions; Figures 6A and B are perspective views, pre- and post- impact, of a gas spring element utilized in an embodiment of the present invention;

Figures 7A to C are diagrammatic illustrations of the operation of the seat incorporating the element of figure 6;

Figures 8A and B are diagrammatic illustrations of a further embodiment of the present invention;

Figures 8C and D are perspective views, pre- and post impact respectively, of a further embodiment of the first aspect of the invention;

Figure 9A is a post-impact side view of a seat according to a further embodiment of the invention; Figure 9B is a detail perspective view of the seat of figure 9A;

Figures 1OA and B are pre- ^• and post-deployment side views of a further embodiment of the invention;

Figures 11A and B are perspective rear detail views, pre- and post-deployment, of a further embodiment of the invention;

Figures HC and D are front perspective views illustrating two different types of support;

Figures 12A and B are side views illustrating the operation of a second aspect of the invention;

Figures 13A and B are perspective views from the rear of a further embodiment of the second aspect of the invention;

Figure 14 is a perspective detail view of figure 13; Figures 15A and B show perspective views of a three point belt implementation in pre- and post-impact conditions respectively;

Figures 16A to C illustrate further seat belt arrangements with which the invention can be used; Figures 17A and B are perspective views illustrating advantageous constructions of the seat with and without seat pan and seat back elements;

Figures 18A to C are perspective views of seat frames supporting various sizes of seat back section.

Figures 19 and 20 illustrate alternative arrangements for supporting a seat in accordance with the present invention; DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Figure IA is a diagrammatic illustration of a seat 10 for supporting an occupant facing in a direction A. The seat incorporates a seat back 12 rotatable about a pivot 16 on a rigid outer frame 14, the axis of the pivot lying substantially transverse to direction A and forward of the H-point of the seat when viewed in that direction. As shown, the axis also lies behind the H-point when viewed in the first direction. Resistance to rotation of the seat back is provided by a linear action spring 20 attached at one end to the base of the deforming back section 12 and at the other end to the seat frame or some other point fixed relative to the vehicle. The spring may alternatively have a rotational action, for example a spiral spring, and may be located around the pivot 16. Seat pan 22 is rotatable on the frame 14 about a pivot 26 having an axis also substantially transverse to the direction A, i.e. parallel to the axis of pivot 14, and located higher, in use, than the H-point of the seat. As shown, the axis also lies below the H-point. Rotation of the deforming seat pan 22 is controlled by a spring element 24 located between the seat pan 22 and the vehicle floor 28 or alternatively incorporated within the pivotal joint 26 as a rotational spring. As illustrated in figure IB, the control means 20,24 allow controlled rotation, indicated by arrows R, of the seat back and seat pan in the event of a significant force being applied to the seat as indicated by arrow F. When deployed, the seat pan typically drops by 10 degrees and the seat back rotates rearward by 8 degrees, although other angles of deployment may be set depending upon the desired response and installation considerations.

Figures 2A and B shows the envisaged occupant response pre- and post-impact respectively. As the seat back 12 and pan 22 rotate, the seated occupant 29 adopts a more favourable seated configuration during impact. In particular, the H-point moves rearwards and, in the case of a pivoted seat pan, lower, resulting in an occupant seating position that can be beneficial in reducing ramping and associated whiplash injuries.

The stiffness of the springs will control the response of the seating system and therefore the occupant's acceleration time history during rear impact events or post frontal impact events (i.e. an occupant rebounding off a deployed front mounted airbag) . The spring control means will also absorb energy transmitted by rotation of the seat pan and the seat back about their respective axes. Seat pan 22 can be connected by a linkage system to the seatback in such a way that its deployment angle is a function of the seatback rotation. Locking devices, e.g. ratchets with quick release handles, can be employed to restrict the seat back, or seat pan to rotation in only one direction, thereby preventing seatback and seat pan rebound and tensioned springs unloading into the occupant.

Moreover, the springs may incorporate adjustment means 30,32 to pre-load the springs so as to resist rotation of the seat pan and the seat back about their respective axes up when in normal use. Only in impact situations, in which the ^• load applied exceeds the preload, will the springs deform further to allow rotation of the seat back and absorb the energy of that rotation.

Where spiral springs are used, these can be secured at one end to a rotating shaft allowing the seated occupant to adjust the amount of tension on the spring. A light occupant, who in the event of a rear end impact has less inertia, only requires some pre-loading of the spring. By winding up the spiral spring and influencing the spring stiffness the seatback and pan section may now support the occupant's load.

Figures 3A and B illustrate dormant and deployed positions respectively of a seat according to the present invention and having a weight adjuster mechanism 32 running under the seat pan 22 to allow the seated occupant to pre-tension a linear motion spring 20 to adjust the rotational properties of the seatback section 12. Figures 3A and B illustrate show how, for a light person, less pretension adjustment is required than that for a heavier person as shown in figures 4A and B. Figures 5A and B are detailed perspective views of the weight adjuster mechanism 30 in low and high pretension positions respectively. The mechanism consists of a threaded shaft 34 carrying a threaded block 36 to which the spring element 20 is attached. As the shaft 34 is turned (arrow T) by use of a handle 38, the block 36 moves forward (arrow U), putting the spring 20 in tension. The spring block 36 runs along a slider guide (not shown) to ensure that that it remains in the correct plane. A mounting structure 40 is required to support the shaft and handle assembly.

The embodiments above illustrate control means employing a spring that is mechanical, i.e. employing a solid elastic element. Figures 6A and B are perspective views, pre- and post-impact respectively, of a spring 42 in which the elastic element is a gas, in this case air.

Spring 42 consists of a top and bottom plate (not shown) that contains an air bag 44 constructed, for example, from a cylinder of heavy-duty elastomer material. Such springs are manufactured e.g. by Continental of Germany and commonly used in cab seat suspension systems (so called ^ΛSitzfedern' ) . The air spring can be inflated to predetermine levels to provide a resistance to the rearward motion of a seated occupant during a rear impact event.

As shown in figure 7A, spring 42 is mounted to the vehicle at 50 and pressurised via air hose 48 by a small compact compressor unit 46, powered e.g. from the vehicle power supply. Inflation can be controlled manually by the seated occupant, or in response to a signal from an embedded sensor switch (not shown) integrated into the supporting seat structure. For a light seated occupant it is envisaged that less pressure is required that that for a heavy occupant. Experiments suggest that the seatback would need to withstand an applied loading of 0.38 kN (based on 70 % th effective mass of a 50 percentile dummy) in the pre- impact condition. For a cylindrical air spring of the kind shown in figure 6A and having a nominal diameter of 40mm, only 3 bar of pressure is required initially, to provide such support during normal use.

In the event of an impact, the seated occupant loads the seat back 12 as indicated by arrow L in figure 7B. In accordance with the invention, seat back 12 rotates in controlled manner determined by the air spring 42. To control the rearward response of the occupant and avoid encroaching on the space of passengers behind the seat, it has been found that the movement of the bottom of the seat back (indicated at ^ΛM" in figure 7B) should preferably be limited to 100mm. For the spring and occupant characteristics mentioned above (inter alia a 70 % th effective mass of the 50 percentile dummy) , this is achieved by an applied force of 1.1 kN corresponding to a

3 g impact. If 100 % effective mass is considered, then the desired forces are achieved when the dummy is exposed to a 2 g impact event. This also assumes a constant increase in the impact magnitude during the initial stages of the impact. If the magnitude varies, i.e. non-linear responses due to changes in vehicle stiffness as a function of vehicle damage, changes in the occupant's effective mass occur, or occupant ramping or rotation will influence the actual moments applied to the seatback and therefore to the air spring.

As with the mechanical system, a method of preventing the deployed inner seatback from imparting the stored elastic energy upon the seated occupant is required. This may be achieved by a control valve (not shown) within the air spring circuit which can exhaust some of the air in the spring once a predetermined load or pressure is reached. As such, the element 42 behaves as a damper using gas as a damping fluid. Not only does this allow the impact energy to be dissipated rather than rebounded on the occupant, it may also allow further compression of the spring without further increase in spring rate. Figure 7C shows a corresponding arrangement for the seat pan 22.

Alternatively or in addition, the control valve may be controlled in response to crash (acceleration) sensors within the seat or elsewhere in the vehicle. Once a signal greater than a predetermined level is detected, the valve opens, allowing air to escape from the spring and the pivoting sections to deploy.

Another energy management concept utilises plastic deformation to control the rotation of the seat back and absorb the occupant's impact energy. Whilst such devices are not reusable and will need to be replaced after each impact event, they have an advantage over reusable mechanical spring and air spring systems in that they can be designed to behave at predetermined loading conditions.

In contrast, the spring and air spring arrangements described above require a degree of manual adjustment in order to set up the spring systems for the optimum system response. Figures 8A and B show a first implementation of the proposed principle in pre- and post-crash conditions respectively. An energy absorbing honeycomb structure 60 is located between the deforming seatback 12 a rigid mounting plate or part of the vehicle structure 50, or integrated into the space below the seat pan (not shown) .

As the occupant loads the seat during the rear impact event, shown by arrow N in figure 8B the honeycomb structure 60 is crushed, absorbing the occupant crash energy and repositioning the seat back 12. The honeycomb structure 60 can be constructed so that it is tailored to the 5^th, 50^th and 95^th percentile occupant. As well as the more traditional honeycomb structures conventionally used for crash absorption, composite elements, in particular cellular beam structures as described in WO0114128, may be considered. The latter structures have the advantage that they can be incorporated into the actual seating structure during production of the proposed frame elements. Figure 8C shows a second implementation of the proposed principle in a pre-impact state. One or more strips 62 of material such as metal are attached between the outer frame 14 and the seat back 12. In the event of an impact, these strips are loaded and yield as illustrated in the detail view of figure 8D. As with the first implementation, the yield properties of the strip may be tailored to a particular range of occupants. For the event that the strip fails completely, some means of preventing the inner seatback 12 from rotating in an uncontrolled manner, e.g. a tether strap (not shown) may also be included.

Figure 9A is a post-impact side view of a further embodiment of a seat according to the present invention and incorporating an insert 70 slidingly mounted at one end in the seat back or, as shown, under the seat pan 22. The other end of the insert 70 is pivotally mounted at 71 to the seat back 12 (or seat pan) and is deployed with the movement of the seat back. The substantially planar insert supports the occupant in a direction substantially perpendicular to its plane, thereby providing the occupant with support in the region between the seat pan and the seat back and preventing uncontrolled occupant drop- through onto the vehicle floor or interior fittings. It will be seen that once the seat back 12 and seat pan 22 are deployed, no gap exists, unlike other proposed ^Λcatchers-mitt' concepts. The embodiment of figure 9 also has a head restraint 72 integrated into the inner seatback 12 and above the rotation axis 16 so that, as the inner seatback section rotates under the occupant's applied load, the backset, i.e. the distance between the front face of the head restraint and the back of the seated occupant's head, is automatically reduced.

Alternatively, the head restraint can be integrated into the outer seat frame 14. Figure 9B is a detailed perspective view of the insert 70 showing rollers 74 on which the insert runs inside the seat pan and the connection links 76 by means of which the insert is connected to the seatback.

Figure 1OA is a pre-deployment side view of a preferred embodiment incorporating the air spring assembly

42 mentioned above. Assembly 42 is connected at one end 77 to seat back 12 via link 78 and supported at its other end

74 to the seat frame or vehicle floor. During a crash, assembly 42 is crushed as illustrated in figure 1OB. Figure HA is detail perspective view from the rear of a further embodiment of the present invention. Rotation of the seat pan 22 is controlled by first pins 79' which abut and are supported by corresponding second pins or supports 79 provided on the rotatable seat back 12. In the example shown, pins 79' and 79 are provided on portions remote from the respective pivots, i.e. at the rear of the seat pan 22 and at the bottom of the seat back 12. As shown in figure HB, rotation of the seat back 12 as a result of an impact (as controlled by air spring 42) causes supports 79 to move rearward, thereby withdrawing support for first pins 79' and allowing seat pan 22 to fall. As indicated by arrow G in figure HB, the Catcher's mitt' motion of the seat results in the creation of a gap in the support provided to the occupant, presenting a possible safety issue. Figure HC illustrates a first solution to this issue, namely a flexible panel 80 attached to the rear end of the seat pan 22 and the bottom end of the seat back 12, thereby providing support to the occupant and ensuring no gap between the seat pan and seat back in their deployed state. In the example shown, the panel is made from webbing material and folded upon itself prior to deployment.

Figure HD shows a second solution to the issue. It is similar to the embodiment of figure 9 in that it employs a seat pan insert 82 mounted slidably in seat pan 22 and attached to the seat back 12 e.g. via a linkage 84. When the seat back 12 deploys to the position shown in figure HD, insert 82 is pulled out by the link bar 84 to ensure that the occupant still has supporting structure to sit on and to ensure that the gap between the rotating seatback and the seat pan is closed. Figure 12 is a similar view to that of figure 9A but illustrating a second aspect of the invention, namely an occupant seat belt anchor configured to move in the opposite direction to the force F (from point 88 to point 88 ' ) .

This is advantageously implemented as shown in the pre- and post-impact perspective views of figures 13A and B, namely by attaching the lower restraint anchorages / anchor points 90 to the sliding seat pan insert 70. This allows the correct positioning of the seat belt 92 to be maintained during all stages of seat deployment. This not only involves motion in the opposite direction to the force but also motion downwards. A detailed perspective view of the insert 70 is shown in figure 14 and incorporates connecting linkage arms 76, two sets of rollers 74 and the anchorage attachment shaft 94.

Although illustrated in figures 13A and B in the context of a lap belt, it will be appreciated that this aspect of the invention is applicable to other seat belt arrangements. Figures 15A and B show perspective views of a three point belt implementation in pre- and post-impact conditions respectively.

It will be appreciated that by ^Λanchor point' is meant any point at which a restraining force is applied to the belt. Thus a three-point implementation of the kind shown in figure 15 may have two lower anchor points on the seat (the belt being fixedly attached to one anchor point and attached by means of a releasable buckle to the other) and one upper anchor point attached to the B-pillar of the vehicle. As is well known, in common 'inertia reel' implementations the belt is typically not fixedly attached to either the buckle or the B-pillar anchor points but instead passes through a loop attached to these points. Such loops apply a restraining force to the seat belt harness in the event of impact yet also allow the seat belt harness to adapt to the occupant. As is well known, tension in the harness is typically maintained by a inertia reel tensioner which is attached at the foot of the B-pillar, below the upper anchor point. As shown in figures 16A-C, all the anchor points 90 of the seat belt may be incorporated into the seat rather than the vehicle, resulting in a restraint system that is fully integrated into the seat. Legislation governing such integrated restraints requires stronger seat structures. However, research has shown that such integration, particularly with four point restraint arrangements of the kind shown in figures 16B and C, can reduce occupant injury in front, rearward, side impact and vehicle rollover.

The seat of the invention can be made using conventional automotive seating materials such as steel.

However, environmental, mass, manufacturing and other benefits may be achieved by making the seat from the fibre-reinforced cellular beam structure according to the aforementioned WO0114128. Corresponding embodiments of the seat frame 14 and seat frame 14 incorporating seat back 12 and seat pan 22 structures are shown in figures 17A and B respectively.

Moreover, a range of seatback designs can be employed to allow the innovative seating system to be tailored for specific applications: Figures 18A to C show seat frames 14 supporting large, medium and small seat back sections 12 respectively. Smaller seat back sections facilitate the inclusion in the frame of one or more cross-members 96 to increase the lateral stiffness of the seat. Front cross- member 97 also increases lateral stiffness

Problems associated with larger, wider or out-of- position occupants adversely interacting with a seat frame are mitigated by the arrangement of figure 19 in which rotatable seat pan 22 and back 12 are pivoted not on a seat frame but rather on first and second posts 101, 102 secured to the floor 103 of the vehicle. Figure 20 illustrates an alternative embodiment in which the seat pan 22 and back 12 are pivotable about arms 111,112 attached to the wall 113 of the vehicle. It will be appreciated that whilst the invention has been described with regard to specific embodiments, it is in no way limited to those embodiments. For example, whilst described in the context of a forward-facing seat for an automobile, it is equally applicable to other kinds of vehicle, e.g. trains, aeroplanes, and to other orientations, e.g. facing rearward relative to the direction of travel. Similarly, whilst the illustrated embodiments involve rotation of the seat back about a physical axis, namely a pivot, the invention includes within its scope embodiments, e.g. using linkages, where rotation is substantially about a virtual axis.

Claims

1. Seat for supporting an occupant in the event of a significant force being applied to the seat in the same, first, direction as the occupant is facing; the seat comprising: a seat back rotatable substantially about a first axis lying substantially transverse to the first direction and higher than the H-point reference of the seat; and control means for allowing controlled rotation of the seat back about said axis in the event of said significant force being applied.

2. Seat according to claim 1 and comprising a seat pan rotatable substantially about a second axis lying substantially parallel to the first axis and forward of the H-point reference of the seat when viewed in said first direction.

3. Seat according to claim 1, wherein the seat pan is kinematically linked to the seat back so that movement of the seat back also results in motion of the seat pan.

4. Seat according to any preceding claim, wherein the control means comprises means for absorbing energy transmitted by rotation of the seat back about the first axis .

5. Seat according to claim 4, wherein the control means is configured to resist rotation of the seat back about the first axis up to a threshold and, above said threshold, to absorb energy of rotation.

6. Seat according to any preceding claim and comprising a pivot about which rotation of the seat back takes place.

7. Seat according to any preceding claim, wherein the control means is connected between the seat back and a point fixable relative to the vehicle.

8. Seat according to any preceding claim, wherein the control means has a rotational action.

9. Seat according to claim 8, wherein the control means is mounted about a respective axis of rotation of the seat pan or seat back.

10. Seat according to any preceding claim, wherein the control means has a linear action.

11. Seat according to any one of claims 7 to 10 and comprising a frame for fixable to the vehicle and about which the seat back can rotate, the control means being connected to the frame.

12. Seat according to any preceding claim, wherein the control means comprises a spring having an elastic element .

13. Seat according to claim 12, wherein the elastic 5 element includes a gas.

14. Seat according to claim 12 or claim 13, wherein the control means comprises a damper.

10 15. Seat according to claim 14 when dependent on claim 13 and wherein the gas acts as a damping fluid.

16. Seat according to claim 15, wherein the spring comprises a gas containing envelope having an exhaust

15 valve configured to prevent damping gas flow until such time as the significant force is applied, thereby allowing the gas to act spring in the meantime.

17. Seat according to claim 16, wherein the valve is 0 configured to be controlled by the pressure in the envelope.

18. Seat according to claim 16, wherein the valve is configured to be controlled by a sensor. 5

19. Seat according to any one of claims 1 to 11, wherein the control means may comprises a plastically deformable element .

20. Seat according to claim 19, wherein the element is configured to deform in compression.

21. Seat according to claim 19, wherein the element is 5 configured to deform plastically in tension.

22. Seat for protecting its occupant in the event of a significant force being applied to the seat in the same, first, direction as the occupant is facing; the seat

10 comprising: a seat back rotatable substantially about a first axis lying substantially transverse to the first direction and higher than the H-point reference of the seat; and an occupant seat belt anchor kinematically linked to 15 the seat back and configured to move in the opposite direction to said first direction in the event of said significant force being applied.

23. Seat according to claim 22 and comprising a seat pan 20 rotatable substantially about a second axis lying substantially parallel to the first axis and forward of the H-point reference of the seat when viewed in said first direction.

25 24. Seat according to claim 23, wherein the seat pan is kinematically linked to the seat back so that movement of the seat back also results in motion of the seat pan.

25. Seat according to any one of claims 22 to 24, wherein the occupant seat belt is configured to move downwards in the event of said significant force being applied.

5 26. Seat according to any preceding claim, wherein the first axis lies behind the H-point reference of the seat when viewed in said first direction.

27. Seat according to any preceding claim, wherein the 10 second axis lies below the H-point reference of the seat.

28. Seat according to any preceding claim and comprising a head restraint located higher than the first axis.

15 29. Seat according to claim 28, wherein the head restraint is attached to said seat back rotatable about said first axis.

30. Seat according to any previous claim and comprising 0 support means configured to support the occupant in the region between the seat pan and the seat back in the event of said significant force being applied.

31. Seat according to claim 30, wherein the support means 5 is attached to the seat pan and/or the seat back.

32. Seat according to claim 31, wherein the support means is slidably mounted within one of the seat pan and seat back and pivotally mounted to the other of the seat pan and seat back.

33. Seat according to claim 32, wherein the support means 5 is substantially planar and is configured to support the occupant in a direction substantially perpendicular to the plane.

34. Seat according to claim 33 when dependent on claim 10 22, wherein the occupant seat belt anchor is attached to the support means .

35. Seat according to any preceding claim and comprising all the anchors for the seat belt.