The invention relates to a seat assembly.

It is known in seats for helicopters to include a shock absorber, similar to an automatic shock absorber, under the seat assembly so that in the event of an accident where the helicopter falls to the ground, some of the shock impact will be absorbed for a seat occupant. It is also known, with the same object, to provide seats in helicopters with legs which are arranged to deform to absorb impact. A problem may arise with both of these known constructions, in that the seat assembly is allowed to drop towards the floor and if another person is sitting behind the seat, their feet or legs may be trapped or injured by it.

According to one aspect of the invention there is provided a seat assembly including a rigid cellular structure, the cellular structure being arranged to absorb impact applied to at least part of the seat by deformation of the cellular structure.

Deformation of the cellular structure can thus absorb impact.

The term "cellular structure" as used herein is intended to encompass both a structure of closed cells and an open cell structure (a sponge being an example of an open cell structure).

The cellular structure may be elongate and may be arranged to absorb impact applied in a lateral direction thereto. Preferably the cellular structure is wall-like in shape and preferably is arranged to absorb impact applied in a direction perpendicular to the plane of the wall.

Preferably, a wall-like structure is provided in a seat base of the seat assembly and is arranged to absorb impact applied downwardly to the seat base. In this way, the seat assembly can absorb impact without the seat base moving downwardly. The term "seat base" as used herein refers to that portion of a seat assembly which a person sits on.

Often in an aircraft seat assembly, the seat base comprises a cushion mounted on a light panel on a rectangular frame supported by legs. In the case of an underside impact to the aircraft, a seat occupant's

SUBSTITUTESHEET

thighs are urged against the front bar of the frame, in particular if the cushion panel breaks, and the seat occupant's thighs may be injured or even broken. It is an important feature of the use of the wall¬ like cellular structure that in such a case the load constituted by the occupant is spread over the wall¬ like cellular structure rather than concentrated at the front frame oar. The wall-like cellular structure thus provides continuous local support and impact absorption. Conveniently the plane of the wall-like cellular structure may be substantially parallel to the support surface of the seat base.

The wall-like cellular structure may in addition, or alternatively the arranged to absorb impact applied to the front of the seat base.

The seat assembly may include a seat back and the wall-like cellular structure may in addition, or alternatively be in the seat back and be arranged to absorb impact perpendicular to the support surface of the seat back. Conveniently, the plane of the wall¬ like cellular structure may be substantially parallel to the support surface of the seat back.

The seat assembly may have a calf support and the cellular structure may in addition or alternatively be

in the calf support and arranged to absorb impact applied to the support surface thereof.

The seat assembly may have a headrest and the cellular structure may be in the headrest and arranged to absorb impact applied to the support surface thereof.

According to another aspect of the invention there is provided a rigid cellular structure for use in a seat assembly according to the first aspect of the invention.

The cellular structure may be provided with a layer on one side or on both sides to form a sandwich.

The cellular structure may take any suitable form and in one preferred embodiment is a honeycomb structure. The honeycomb structure and/or the layers may be made from any suitable material and may be made from metal sheet, such as aluminium. Where the cellular structure is in a sandwich this may then be the known aluminium honeycomb sandwich. One such sandwich is disclosed in WO/GB89/00897. The honeycomb structure and/or the layers may be made from a composite material such as kevlar or carbon fibre. In another embodiment, the structure may be a foam which may be, for example, urethane foam, or the new

aluminium foam material such as disclosed in US 4973358.

In known aircraft, seats are normally forward facing. In the event of an accident involving frontal impact, passengers in the seats are thrown forwards, away from the seat. Rearwardly facing seats could be used, such that passengers in a frontal seat impact would be forced back against their seats and not thrown forwards, but there is then the problem that on take¬ off and climb of the aircraft, both acceleration of the aircraft and gravity are acting in the direction to urge a passenger out of his seat.

According to another aspect of the invention there is provided a seat assembly for use as a passenger seat in an aircraft, the seat assembly including a seat base, the seat base being tiltable backwards.

A passenger can thus sit up normally in the seat assembly when the aircraft is travelling levelly or descending and the seat base can be tilted backwards for take off or climb so that a passenger is not urged out of the seat.

According to another aspect of the invention there is provided an aircraft including a rearwards facing seat

comprising a seat base, the seat base being tiltable backwards.

The seat may also include a seat back which may also be tiltable backwards.

The seat back and seat base may be separately tiltable, but preferably are connected so as to be tiltable together. A structural member of the seat base may be integral with a structural member of the seat back such that the seat back and seat base are tiltable together.

The seat base may be tiltable to an angle of between 15° and 30° to the horizontal and preferably is tiltable to an angle of between 20° and 25°.

A foot rest may be provided for use when the seat base is tilted.

Where an aircraft is involved in a frontal impact and a passenger is in a rearwardly facing seat, the applicants have found that there is a tendency for the lower part of the legs and feet to be thrown back under the seat. Preferably therefore a calf support is provided.

Indeed according to a further aspect of the invention there is provided a seat assembly for use as a rearwardly facing seat in an aircraft, the seat

including a calf support.

According to another aspect of the invention there is provided an aircraft including a rearwards facing passenger seat, the seat including a calf support.

The calf support may be dimensioned to support at least half of th≤ length of the calf of a seat occupant and the position of the calf support in relation to the seat base may conveniently be adjustable. Otherwise, the calf support may extend downwardly from the front edge of the seat base and in an alternative embodiment the calf support is dimensioned to support substantially the whole length of the calf.

Another problem identified by the applicants in the use of rearwards facing seats in aircraft is that in the case of a frontal impact, the arms of a passenger tend to be thrown outwards and backwards from him. The seat assembly therefore preferably includes arm rests including portions arranged to inhibit outwards sliding of an occupant's arms off the arm rests.

According to another aspect of the invention, there is provided a seat assembly for use as a rearwards facing passenger seat in an aircraft, the seat assembly

including arm rests having portions arranged to inhibit outward sliding of an occupant's arms off the arm rest.

According to a further aspect of the invention, there is provided an aircraft including a rearwards facing passenger seat assembly, the seat assembly including arm rests including portions arranged to inhibit outwards sliding of an occupant's arms off the arm rests.

Each said portion may suitably comprise an upstanding ridge along or adjacent the edge of each arm rest.

The seat assembly preferably includes a head rest which extends from the top of the seat back to above the top of the head of a seat occupant.

The seat assembly preferably includes portions on each side of the seat back to inhibit sideways sliding of the body of an occupant.

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

Fig. 1 is a side elevation of the first embodiment. Fig. 2 is a fragmentary detail view of the sandwich of the first embodiment,

Fig. 3 is a side elevation cross-section of the second embodiment,

Fig. 4 is a perspective view of the third embodiment, Fig. 5 is a side elevation of the third embodiment, Fig. 6 is a side elevation of the third embodiment in a tilted position,

Fig. 7 is a perspective view of the fourth embodiment. Fig. 8 is a side elevation of the fourth embodiment, Fig. 9 is a perspective view of the fifth embodiment,

Fig. 1 shows the first embodiment. In the seat assembly 60, the seat base padding 61 and seat back padding 62 are integral and are mounted on an aluminium honeycomb sandwich 63 which follows the desired contour of the support surfaces 64, 65 of the seat back padding 62 and seat base padding 61. The front surface 66 of the seat base in this context is considered a support surface and the honeycomb sandwich 63 follows the contour thereof. A calf support 67 is also provided in the form of padding 68 mounted on a honeycomb panel 69. A fragmentary detail view of the aluminium honeycomb sandwich 63 is shown in Fig. 2. The panel consists of two parallel outer layers 70 of the aluminium sheet having further

impact, the body of an occupant is forced against the seat assembly and the walls 71 of the hexagonal cells collapse absorbing impact energy and reducing the likelihood of injury to the occupant.

The walls of the hexagonal cells may be made of aluminium which is between 17μm and 64μm having a side wall length of between 5.2mm and 11.0mm a cell height of 25mm and a density for the structure if between 16kgm ^"3 and 29kgm ^"3 . The facing layer thickness may be 0.5mm. In tests using such honeycomb and applying a test load of between 2000N and 9000N over an area 200 x 360mm the honeycomb crushed satisfactorily.

In another embodiment foamed aluminium may be used in place of the honeycomb. A framed aluminium with a density of about 54kgm ^"3 would be suitable.

In another embodiment, the headrest of the seat assembly may also be formed as padding on an aluminium honeycomb sandwich.

Fig. 3 shows an embodiment which can be used in existing aircraft seats. Thus the seat assembly 60 comprises a seat frame 72 made from connected tubular steel bars. The bars normally support light panels. Fig. 3 shows a light panel 73 which is attached to two

steel bars. The bars- normally support light panels. Fig. 3 shows a light panel 73 which is attached to two parallel transverse bars 74 to form a back panel of the seat around which the back padding 62 is provided. In the embodiment, a light panel, which is normally supported on two front and rear transverse bars 75 in the base of the seat, is removed and an aluminium honeycomb panel 76 is inserted instead. This may necessitate some cutting of the seat base padding 61. The panel 76 may be flat or may be contoured to the support surface 65 of the seat base padding 61.

In existing seats, in a downward crash, as discussed, the light base panel often breaks so that the forces on a seat occupant are concentrated at the front and rear transverse bars 75. This may result in femoral and tibial fractures and also in excessive lumbar loading over the limit defined in the new Survivability Regulations for Impact (FAA AC25.562.1). By means of the honeycomb panel distributed rather than localised support is provided to reduce the risk of injury to a seat occupant.

In the third embodiment, a rearwardly facing passenger seat for an aircraft 10 includes a seat base 11 and a seat back 12. Arm rests 13 are provided. From the front of the seat base 11, a calf support 14 extends

downwardly and at a slight forward angle. The calf support is of the same width as the seat base 11 and extends down to about the level of the top of the person's heel. The calf support 14 includes a central rectangular aperture which is elongate in the width direction of the calf support 14.

The seat back 12 of the seat assembly 10 is relatively broad in the shoulder area to ensure that it extends across the total width and height of an occupant's shoulders. At each side edge of the seat back 12, a ridge 16 extends forwardly.

A headrest 17 extends upwardly from the seat back 12. The headrest 17 also includes forwards projecting ridges 18 along its side edges.

In use, then, the calves of a seat occupant are supported by the calf support 14 so that they cannot be thrown back under the seat assembly in the event of a frontal impact on the aircraft. The seat occupant's shoulders are also supported by the seat back 12 and the ridges 16 prevent the occupant from sliding sideways out of the seat. Similarly, the ridges 18 on the headrest 17 ensure that the head is not thrown sideways off the headrest in an impact.

At either side of the seat assembly, in a position corresponding to the notional line on which the seat back and seat base meet, an outwardly extending spigot 19 is provided. Each spigot 19 is received in a bore in a seat mounting, the seat mounting including a locking mechanism (not shown) by means of which the seat assembly can be locked in two positions. In the first, normal position, the seat base 11 is horizontal or tilted backwards slightly. This is the position which the seat assembly will be in when the aircraft is travelling levelly. The mechanism also locks the seat assembly in the second position in which the entire seat assembly 10 is tilted backwards at an angle of 22.5° to the horizontal line and this is the position the seat assembly will be in for take-off and climb of the aircraft. As shown in Fig. 3, during climb of the aircraft the seat assembly is at a similar angle to the vertical as when in the normal position and the aircraft is travelling levelly. A footrest 20 is provided for use by the occupant when the seat assembly is in the tilted position. This may be carried by the seat assembly in front.

In other embodiments, the angle of the seat back and seat base may be adjusted independently, so that, for example, the seat back can be reclined without tilting of the seat base, if desired.

Figs. 7 and 8 show the fourth embodiment. The fourth embodiment is similar to the third and only the differences from the third embodiment will be described. The same reference numerals will be used for equivalent features.

The seat assembly 10 in the fourth embodiment is fixedly mounted by a seat mounting 21. The seat mounting 21 comprises a base 22 which extends under the seat assembly and is secured to the floor of the aircraft, and two arms 24 which extend from either side of the base 22 up to the calf support 14.

Along the outer edge of each arm rest 13 is provided a raised ridge 23.

In use, a seat occupant's arm lie on the arm rests 13 inwardly of the ridges 23. In the event of a frontal impact for the aircraft, the ridges 23 restrain a seat occupant's arms from being thrown outwardly and backwards with resultant injury to the occupant.

Fig. 9 shows the fifth embodiment which again is a rearwardly facing aircraft passenger seat. The seat assembly 30 comprises a shell 31 which mounts a seat base 32, a seat back 33 and two arm rests 34. The

seat base and the seat back are separate padded panels. The seat base 32 can be mounted on the shell 31 in a number of positions such that the seat base can be moved forwards or backwards to accommodate different thigh lengths for seat occupants and ensure that the front of the seat is in contact with the back of the occupant's knees. Similarly, the seat back 33 is adjustable upwardly and downwardly to be secured in different mounting positions on the shell 31 to accommodate different shoulder heights, the seat back 23 being extended at the shoulder region to be broader than the width of an occupant's shoulders. A calf support 35 is provided in the form of a padded member which is of a similar width to the seat base 32 and which is mounted on an arm 36 which extends from the underside of the shell 31. The arm 36 is pivotally connected to the shell 31 such that the calf support 35 can be pivoted to suitably contact and support occupant's legs of different length.

The seat assembly 30 has a headrest 37 which is adjustable for height again to ensure that it gives the best possible support.