Patent Description:
Seat backs or seat back assemblies for providing support to a seat occupant are well known. The provision of suitable support in a seat structure, particularly for use in a vehicle, is important to limit the likelihood of harm or discomfort to a seat occupant.

Seating systems intended for use in aircraft preferably possess qualities or characteristics which are particularly appropriate for the aircraft environment. For example, they may be configured to absorb vibration or intermittent shock loads caused by turbulence. A seat back assembly intended for use as part of an aircraft seating system must pass rigorous safety tests to ensure that it is sufficiently strong to withstand not just heavy use, but also potentially extreme conditions such as may arise in the unlikely event of an aircraft impact. Furthermore, seat assemblies should be configured so that in the event of an impact, the effect on occupants of the aircraft seats is minimised.

Although numerous seat back designs are known, there is still a need to improve the previously proposed designs, in particular to provide a seat back assembly for a vehicle seat which is more robust and provides enhanced safety for a passenger.

<CIT> discloses a seat energy absorption device that has a seat energy absorption unit that uses a sliding connection connected to the base of the seat to absorb primary acceleration movement of a backrest unit in a crash situation.

Arrangements of the present invention seek to provide an improved seat assembly for a vehicle seat, in particular for an aircraft seating system.

According to an aspect of the present invention, there is provided a seat assembly as set out in claim <NUM> below. In embodiments of the invention, an upper portion of the seat back assembly (e.g. above the upper seat back fixing) rotates or move with a component in a forwards direction responsive to the predetermined force being applied to the rear of the seat back assembly.

This configuration enables an upper portion of the seat back assembly to rotate forwards in the event that a predetermined force is applied to the seat back assembly. The predetermined force may be a force corresponding to a head impact (HIC) event. The movement of the seat back assembly in this manner reduces the deceleration of the head of an occupant in the seat behind the seat back assembly and facilitates head slide and reduces neck rotation during a HIC event.

The lower seat back fixing comprises a link which limits movement of the seat back assembly relative to the support frame. The link may therefore be configured to restrict the relative motion of the seat back assembly and the support frame in order that the seat back assembly is not over tilted.

The link may be attached at one end to the seat back assembly and at the other end to the support frame, the friction assembly acting on the link to prevent it moving in normal use.

The friction assembly may apply an adjustable clamping force to the link and may be attached to the seat back assembly or the support frame.

The friction assembly may comprise Belleville washers. The Belleville washers may be mounted on a collar comprising a tubular portion which supports the washers and a flange which applies the clamping force to the link.

The link is attached to the seat back assembly or the frame by means of a sliding connection which allows the link to translate as well as rotate. The link may be configured to translate substantially in a downward direction at the sliding connection and to rotate. This movement of the linkage increases a distance in a horizontal direction between the seat back assembly and the support frame below the upper seat back attachment, so that the seat back assembly above the upper seat back attachment is able to move in a forwards direction.

The sliding connection may comprise a slot in the seat back assembly and a linkage pin connected to the link, wherein the linkage pin is configured to be movable in the slot.

The link may be connected to the support frame by a rotatable connection which allows the link to rotate relative to the support frame.

The seat assembly may further comprise a restoring mechanism configured to oppose the movement of the seat back assembly relative to the support frame. The restoring mechanism may be mounted in the lower seat back fixing.

The restoring mechanism may comprise a resilient element such as an elastomeric element or a spring.

Advantageously, the restoring mechanism may provide an additional securing force preventing the seat back from being too easily pushed forward. The restoring mechanism may also assist in resetting the seat to its normal position.

The link may be aligned with a longitudinal axis of the support frame in normal use, so that the lower seat back fixing is kept as compact as possible and is concealed between the seat back assembly and the seat frame.

To avoid unnecessary duplication of effort and repetition of text in the specification, certain features are described in relation to only one or several aspects or embodiments of the invention. However, it is to be understood that, where it is technically possible, features described in relation to any aspect or embodiment of the invention may also be used with any other aspect or embodiment of the invention.

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:.

In the event of an impact of an aircraft, for example in a crash landing, the abrupt deceleration of the aircraft caused by the impact will cause the occupants to pitch forwards, often causing a collision of a head of an occupant with the seat directly in front of them. Such events are termed head impact events (HIC event). A collision of the head or upper body of a person with the seat directly in front of them may result in significant injury or trauma to the person. It is therefore desirable to design a seat assembly which reduces the likelihood or severity of injury to a person during a HIC event.

<FIG> illustrates a seat assembly <NUM> according to an example. As is shown in this Figure, the seat assembly <NUM> comprises a support frame <NUM>, a seat back assembly <NUM>, an upper seat back fixing <NUM> and a lower seat back fixing <NUM>. The upper seat back fixing and the lower seat back fixing are configured to connect the seat back assembly <NUM> to the support frame <NUM>.

The upper seat back fixing <NUM> comprises a rotatable connection between the seat back assembly <NUM> and the support frame, and the lower seat back fixing comprises a friction assembly <NUM> configured to hold the seat back assembly <NUM> in position relative to the support frame <NUM> in normal use and to allow the seat back assembly <NUM> to move relative to the support frame <NUM> responsive to a force greater than a predetermined force being applied to the seat back assembly <NUM>.

The seat back assembly <NUM> may comprise various components such as a seat cushion, a support frame, and so on. The support frame <NUM> may be formed of various components joined together or may be integrally formed. The support frame <NUM> is connectable to a floor of the aircraft cabin using conventional fixings.

In an example, the input load (e.g. the predetermined force) which causes the friction assembly <NUM> to allow the seat back assembly <NUM> to pivot may be in the region of 400N (e.g. 350N- 700N). In such an example, the distance between the upper seat back fixing <NUM> at which the seat back assembly <NUM> is configured to pivot and the lower seat back fixing <NUM> is approximately <NUM>. The distance between the location at which the input load is applied and the upper seat back fixing <NUM> is approximately <NUM>. The load multiplier of such a configuration is approximately <NUM> times, so that the reaction (friction) load incident on the friction assembly <NUM> is approximately 1727N. The coefficient of friction of the friction assembly <NUM> at the release point is approximately <NUM> in this example. It will be appreciated that the coefficient of friction may vary depending on the materials used. The normal clamping force at the friction assembly <NUM> may be approximately 2500N.

It will be appreciated that the particular values used here are exemplary and different parameters may be used depending on requirements such as a load at which the friction assembly <NUM> should release the seat back assembly <NUM>. The values may therefore further depend on material selection and installation geometry.

The input force which causes the seat back assembly <NUM> to rotate forwards as described above may be set lower than an abuse load. An abuse load is a load at which the force applied to the seat assembly is a result of mistreatment of the seat, rather than a HIC event. If the input force which causes the seat back assembly <NUM> to rotate forwards is set lower than an abuse load, a release mechanism of the friction assembly <NUM> can inadvertently be triggered during application of an abuse load. This may be problematic if the seat back assembly <NUM> is caused to rotate forward unnecessarily, for example, by a child kicking the seat. However, as is described later, the seat assemblies <NUM> described herein may be advantageously further configured to be reset after an abuse event.

<FIG> shows a schematic illustration of a seat assembly <NUM> according to an example. In particular, the seat assembly <NUM> comprises a seat back assembly <NUM> and a support frame <NUM>. The seat back assembly <NUM> further comprises an upper seat back fixing <NUM> and a lower seat back fixing <NUM> which are configured to connect the seat back assembly <NUM> to the support frame <NUM>. The upper seat back fixing <NUM> provides a rotatable connection between the seat back assembly <NUM> and the support frame <NUM>, and the lower seat back fixing <NUM> comprises a friction assembly <NUM> configured to hold the seat back assembly <NUM> in position relative to the support frame <NUM> in normal use and to allow the seat back assembly <NUM> to move relative to the support frame <NUM> responsive to a predetermined force being applied to the seat back assembly <NUM>.

The lower seat back fixing <NUM> of this example comprises a link <NUM> rotatably mounted to the seat back assembly <NUM> and the support frame <NUM> and controlled by the friction assembly <NUM>. The link <NUM> allows limited movement of the seat back assembly relative to the support frame. The support frame <NUM> is connected to the seat back assembly <NUM> via a first pin <NUM>. The first pin <NUM> is rotatably connected to the link <NUM> by a bolt <NUM> which passes through a bore <NUM> provided in a first end of the link <NUM>. The pin <NUM> connects the link <NUM> to the support frame <NUM>. The support frame <NUM> is also connected to the seat back assembly <NUM> via a second pin <NUM> which connects the support frame <NUM> to the seat back assembly <NUM> at the upper seat back fixing <NUM>. The upper seat back fixing <NUM> comprises a retention plate <NUM> configured to retain the second pin <NUM> in position. In this example, the second pin <NUM> is received in an opening/slot in the seat back assembly <NUM> and is retained in the opening by the retention plate <NUM>.

<FIG> provides a more detailed view of the connections between the seat back assembly <NUM> and the support frame <NUM> shown in <FIG>. The seat back assembly <NUM> is able to rotate relative to the support frame <NUM> at the upper seat back fixing <NUM>. The retention plate <NUM> of the upper seat back fixing is fixed to the seat back assembly <NUM> by a pair of releasable fixings such as a bolts or screws <NUM>, <NUM> which are fixed into the seat back assembly <NUM> through a fixing hole and fixing slot formed in opposite ends of the retention plate <NUM>.

The lower seat back fixing <NUM> comprises a sliding connection <NUM> between an upper end of the link <NUM> and the seat back assembly <NUM>. The link <NUM> is mounted to the seat back assembly <NUM> by the siding connection <NUM> and to the support frame by the friction assembly <NUM> and by a bolt <NUM> screwed into the first pin <NUM> through an opening in a lower end of the link <NUM>.

The sliding connection <NUM> comprises a slot <NUM> formed in a wall <NUM> of the seat back assembly <NUM> and a linkage pin <NUM> which is fixed to the link <NUM> and is slideably received and captive in the slot <NUM>.

As can be seen in this example, the upper seat back fixing <NUM> and the lower seat back fixing <NUM> are arranged substantially in line with the support frame <NUM> in normal use (e.g. substantially in line with the wall <NUM> of the seat back assembly <NUM>). For example, the upper seat back fixing <NUM> and the lower seat back fixing <NUM> may be provided substantially along a centreline of the wall <NUM> of the seat back assembly <NUM>. This provides a compact design for the seat assembly <NUM> while providing the benefits associated with the selectively releasable lower seat back fixing <NUM> described below.

In the illustrated embodiment, the friction assembly <NUM> comprises a clamping arrangement which clamps the link <NUM> in normal use and allows the link <NUM> to slide out of the friction assembly <NUM> when a force greater than a predetermined force is applied to the seat back assembly <NUM>.

In particular, the predetermined force may be a force similar to that applied to a seat back assembly <NUM> in a head impact (HIC) event. In the event of a collision of the aircraft, the head of an occupant of a seat arranged in the aircraft directly behind the seat comprising the seat back assembly <NUM> described herein may impact with the seat back assembly <NUM>. Due to the location of the head relative to the seat, the impact is likely to be in an upper half of the seat back assembly <NUM>. The force with which the occupant's head may impact the seat in front of them may cause them significant injury. To alleviate this concern, the configurations described herein, in the event of a predetermined force being applied to the back of the seat back assembly <NUM>, enable the friction assembly <NUM> to release the link <NUM>, so that the seat back assembly <NUM> can rotate about the upper seat back fixings <NUM> and the upper portion of the seat back assembly <NUM> (e.g. above the upper seatback fixings <NUM>) is able to tilt forwards increasing the time over which the impact is absorbed through the seat assembly <NUM> and thereby reducing the deceleration and likely severity of injury. As mentioned above, the link <NUM> is rotatably mounted at one end to the support frame <NUM> and at the other end to the seat back assembly <NUM>, so even after it has been released from the friction assembly <NUM>, it serves to limit the movement of the seat back assembly <NUM> relative to the support frame <NUM>, so that the seat back assembly <NUM> is not over tilted and thereby is prevented from causing an injury to the passenger sitting on that seat.

The mechanisms described herein operate to reduce the deceleration of the head of an occupant in the seat behind the seat back assembly <NUM> and facilitate head slide and reduce neck rotation during a HIC event. In addition, the use of the link <NUM> protects the passenger in the seat in front from injury as the amount that the seat back assembly <NUM> can pivot forward is limited by the link <NUM>. Thus, the examples described herein may serve to prevent or lessen or prevent injury to both the passenger in the seat and the passenger in the seat behind, in the event of a HIC event.

<FIG> illustrates an example of the relative movement of the different components of the seat assembly in the event of greater than a predetermined force being applied to the seat back assembly, for example a force approximating to the force encountered in a HIC incident. <FIG> is a side view and <FIG> is a perspective view of the the upper seat back fixing <NUM> and the lower seat back fixing <NUM> in a normal use configuration in which the friction assembly <NUM> holds the link <NUM> such that it is substantially parallel to the seat back assembly <NUM> and the support frame <NUM>.

<FIG> is a side view and <FIG> is a perspective view of the the upper seat back fixing <NUM> and the lower seat back fixing <NUM> in an overload configuration in which a force greater than a predetermined force (sufficient to cause the friction assembly to release the link <NUM>) is applied to the seat back assembly - for example during a HIC event. In this configuration, the resistance of the friction assembly has been overcome and the link <NUM> has slipped forward out of the friction assembly. At the same time the linkage pin <NUM> has travelled down the slot <NUM> substantially in the direction <NUM> allowing a lower end of the seat back assembly to swing away from the support frame <NUM> and the upper end of the seat back assembly <NUM> to pivot forwards in the direction <NUM>.

<FIG> illustrate a configuration of the seat at the final stage of a HIC event in which the linkage pin has reached the end of its travel because it has bottomed out in the slot <NUM>. The link <NUM> can therefore move no further and it acts to constrain the seat back assembly <NUM> from pivoting further about the upper seat back fixings <NUM>.

<FIG> is a cross section through the link <NUM> and the three distinct fixings which control its articulation. In the illustrated embodiment, the link <NUM> comprises a flat steel plate, but it may take other forms, for example, it may be tubular and may be formed from other materials such as aluminium or carbon fibre.

The upper fixing comprises the linkage pin <NUM> which passes through an opening in an upper end of the link <NUM> and through a collar <NUM> and nut <NUM>. The slot <NUM> which is formed through the wall <NUM> of the seat back assembly <NUM> is keyhole shaped and comprises an enlarged portion and a narrower portion. The enlarged portion is large enough to allow the nut <NUM> and collar <NUM> to pass through. When the link <NUM> is pulled downwardly, the collar becomes captive in the narrower portion of the slot <NUM> so that the linkage pin <NUM> is prevented from being pulled from the slot. The linkage pin <NUM> is not a tight fit in the slot and so is free to rotate and to slide in the slot.

The lower fixing comprises a bolt <NUM> screwed through a hole in the link <NUM> into a threaded bore <NUM> formed in a lower end of the first pin <NUM>. This arrangement creates a rotatable connection between the link <NUM> and the support frame <NUM>.

The intermediate fixing comprises the friction assembly <NUM>. The friction assembly <NUM> comprises a bolt <NUM> such as a machine screw screwed into a second nut <NUM>. The bolt <NUM> passes through a friction collar <NUM> which supports a stack of Belleville washers <NUM> which are held in place by a plain washer <NUM> disposed between the stack of Belville washers <NUM> and the nut <NUM>. The collar <NUM> passes through the cut out <NUM> in the link <NUM> and through the wall <NUM> of the seat back assembly <NUM>, so that when the nut <NUM> is tightened onto the bolt <NUM>, thereby compressing the stack of Belleville washers <NUM>, the link <NUM> is held firmly against the wall <NUM> of the seat back assembly <NUM> under the action of the compressed stack of Belleville washers <NUM>.

The length of the collar <NUM> is carefully selected so that when the nut <NUM> is tightened onto the bolt <NUM> and the washer <NUM> bottoms out against the collar <NUM>, the desired load is applied by the stack of Belleville washers <NUM> to achieve the desired frictional resistance between the collar <NUM> and the link <NUM>. This then sets the load which must be applied to the seat back assembly <NUM> to cause the link <NUM> to be released from the friction assembly <NUM>.

A shoulder <NUM> is formed on the collar <NUM>. The shoulder <NUM> is slightly smaller than the thickness of the link <NUM>, so that when the link <NUM> has been released from the friction assembly and the shoulder <NUM> contacts the wall <NUM> of the seat back assembly, a gap remains between the collar <NUM> and the wall <NUM> of the seat back assembly. This allows the link <NUM> to be more easily pushed back under the collar <NUM> when the seat back assembly <NUM> is reset back into its normal operating position after an unintended release of the link <NUM>, which might occur in the case of a sufficiently high abuse load being applied to the seat back.

As noted above a cut out <NUM> is formed in the link <NUM>. The cut out <NUM> is sized to fit closely around the shoulder <NUM> and to allow the link <NUM> to be clamped across substantially its full width by the friction collar <NUM> under the action of the stack of Belleville washers <NUM>.

By adjusting the number and orientation of the Belleville washers, the clamping/friction force applied to the link <NUM> can be adjusted, thereby altering the predetermined force applied to the rear of the seat back assembly <NUM> which will cause the link to slide free of the friction assembly <NUM>.

The seat assembly <NUM> may further comprise a restoring mechanism <NUM> configured to provide a force to at least partially restore the seat back to its normal operating position.

<FIG>, show various stages in the action of the restoring mechanism <NUM>. <FIG> show the same stages from inside the seat back assembly <NUM>. The restoring mechanism comprises a resilient element <NUM>, which in the illustrated embodiment is a block of elastomeric material but may, for example, comprise a spring. The block of elastomeric material <NUM> may act between the moveable linkage pin <NUM> and the stationary bolt <NUM> or another stationary abutment which may be formed on or fixed to the wall <NUM> of the seat back assembly <NUM>. Thus, when a load over a predetermined load is applied to the seat back assembly <NUM>, the link <NUM> is released from the friction assembly <NUM> and the linkage pin <NUM> begins to move downwardly, guided by the slot <NUM>. As the linkage pin <NUM> moves closer to the stationary bolt <NUM>, the elastomeric block <NUM> is compressed. When the force applied to the seat back assembly <NUM> subsides, the elastomeric material <NUM> recovers and moves to assume its original shape, thereby pushing the linkage pin <NUM> away from the bolt <NUM> and causing the link <NUM> and seat back assembly <NUM> to move back at least partially to their normal operating positions.

If the force applied to the seat back assembly <NUM> is from an HIC incident, the at least partial return of the seat back assembly <NUM> to its normal operating position when the HIC incident ends is helpful in that it increases the space available for the passenger to get out of the seat and evacuate the plane. Similarly, if the force applied to the seat back assembly <NUM> is an abuse load, the at least partial return of the seat back assembly <NUM> to its normal operating position, is helpful to cabin crew or ground crew in resetting the friction assembly and getting the seat back into use.

<FIG> show an alternative restoring mechanism comprising an elastomeric block <NUM> which is loaded in tension. In this embodiment bores <NUM>, <NUM> are formed in the ends of the elastomeric block <NUM>. The free end of the linkage pin <NUM> is inserted into the lower bore <NUM> and a cantilever pin <NUM> which is fixed to the wall <NUM> of the seat back assembly <NUM> is inserted into the upper bore <NUM>. Thus, when a load over a predetermined load is applied to the seat back assembly <NUM>, the link <NUM> is released from the friction assembly <NUM> and the linkage pin <NUM> begins to move downwardly, guided by the slot <NUM>. As the linkage pin <NUM> moves further away from the cantilever pin <NUM>, the elastomeric block is stretched, thereby generating a restoring force in the elastomeric block which is applied to the linkage pin <NUM>. When the force applied to the seat back assembly subsides, the elastomeric element contracts back towards its original shape, thereby pulling the linkage pin <NUM> towards the cantilever pin <NUM> and causing the link <NUM> and seat back assembly <NUM> to move back at least partially to their normal operating position.

The friction assembly <NUM> described herein is configured to be easily reset. Thus, in the event of activation due to abuse, it is possible to reset the friction assembly without replacing components. Furthermore, the resistance to movement provided by the restoring mechanism <NUM> ensures that the seat back assembly is compliant with the industry standard requirement that the seat back is "not easily pushed forward".

The examples set out herein describe the components of the seat assembly in relation to one side of the seat. For example, as is shown in <FIG>, the components described above are arranged on a right hand side of the seat assembly. The opposing side of the seat assembly (e.g. the left hand side) may comprise the same components as described in relation to the right hand side, arranged in a mirror fashion. Thus, one seat assembly <NUM> as shown in <FIG> may comprise two upper seat back fixings <NUM> and two lower seat back fixings <NUM>.

Where components are described in relation to a "side" of the seat assembly <NUM> or seat back assembly <NUM> herein, a side refers to a face which extends substantially perpendicular to a face of a seat assembly which will be in contact with an occupant during use. Where used herein, an "upper portion" of a seat back assembly is a region in an upper half of a seat back assembly or a region above a predetermined point, such as a pivot point. Furthermore, the examples herein are described in relation to a seat assembly <NUM> which is in use with the seat back assembly <NUM> in an upright, or substantially vertical orientation. The "front" of the seat is a face which is in contact with an occupant during use, and a forwards direction is a direction which an occupant will be facing when sitting in the seat. The "back" of the seat is a face of the seat opposite to the front face of the seat. As described herein, the predetermined force may be applied to a back of the seat with a component in a forward direction.

In an alternative arrangement illustrated in <FIG>, the slot <NUM> is formed in the link <NUM> and the linkage pin <NUM> is fixed to the seat back assembly <NUM>. Also, as illustrated in <FIG>, the friction assembly <NUM> comprises one or more Belleville springs <NUM> provided on each side of the link <NUM>, and hence the friction assembly <NUM> applies an even clamping force to both sides of the link <NUM> when the nut <NUM> is tightened onto the bolt <NUM>.

This arrangement works in exactly the same way as the previous arrangement of <FIG>, with the friction assembly <NUM> fixed to the seat back assembly and received in a cut out <NUM> in the link <NUM> so that it clamps the link <NUM> under the action of the Belleville springs <NUM> and prevents the link <NUM> from moving in normal use of the seat. In an overload condition, such as might occur in a crash, the frictional force of the friction assembly <NUM> is overcome, thereby releasing the link <NUM> and enabling the seat back assembly <NUM> to rotate about the upper seat back fixings <NUM> and the upper portion of the seat back assembly <NUM> (e.g. above the upper seat back fixings <NUM>) is able to tilt forwards increasing the time over which the impact is absorbed through the seat assembly <NUM> and thereby reducing the deceleration and likely severity of injury. As mentioned in relation to the previous arrangement, the link <NUM> is rotatably mounted at one end to the support frame <NUM> and at the other end to the seat back assembly <NUM>, so even after it has been released from the friction assembly <NUM>, it serves to limit the movement of the seat back assembly <NUM> relative to the support frame <NUM>, so that the seat back assembly <NUM> is not over tilted and thereby is prevented from causing an injury to the passenger sitting on that seat.

Claim 1:
A seat assembly (<NUM>, <NUM>) comprising a support frame (<NUM>, <NUM>), a seat back assembly (<NUM>, <NUM>), an upper seat back fixing (<NUM>, <NUM>) and a lower seat back fixing (<NUM>), the upper seat back fixing (<NUM>, <NUM>) and the lower seat back fixing (<NUM>) configured to connect the seat back assembly (<NUM>, <NUM>) to the support frame (<NUM>, <NUM>), wherein:
the upper seat back fixing (<NUM>, <NUM>) comprises a rotatable connection between the seat back assembly (<NUM>, <NUM>) and the support frame (<NUM>, <NUM>); and
wherein the lower seat back fixing (<NUM>) comprises a friction assembly (<NUM>, <NUM>) configured to hold the seat back assembly (<NUM>, <NUM>) in position relative to the support frame (<NUM>, <NUM>) in normal use and configured to allow an upper portion of the seat back assembly (<NUM>, <NUM>) to move in a forward direction relative to the support frame (<NUM>, <NUM>) in response to greater than a predetermined force being applied to the seat back assembly (<NUM>, <NUM>),
wherein the lower seat back fixing (<NUM>) comprises a link (<NUM>, <NUM>) which limits movement of the seat back assembly (<NUM>, <NUM>) relative to the support frame (<NUM>, <NUM>), characterised in that the link (<NUM>, <NUM>) is attached to the seat back assembly (<NUM>, <NUM>) by means of a sliding connection which allows the link (<NUM>, <NUM>) to translate as well as rotate.