Field of the Invention

The present invention concerns aircraft seats. More particularly, but not exclusively, this invention concerns an aircraft seat comprising a cushion, wherein the cushion is at least partly formed by a resilient monolithic lattice structure.

Background of the Invention

An aircraft seat cushion typically requires different firmness values in different regions of the cushion. Aircraft seat cushions are typically manufactured from a polymer foam and the variable firmness is usually achieved by joining together foam blocks of differing elastic stiffness using an adhesive. Such cushions therefore comprise abrupt stiffness changes at the interface between neighbouring foam blocks.

Where a more gradual change of stiffness throughout the cushion is desirable, several foam blocks of gradually varying elastic stiffness can be bonded together. For example, a seat pan cushion may have a relatively firm base layer at the bottom of the seat pan cushion, a relatively soft seating layer at the top of the seat pan cushion, and a foam layer of intermediary stiffness positioned between the base layer and the seating layer. Increasing the number of foam blocks within a cushion increases the manufacturing time and costs associated with producing the cushion. Furthermore, there is an undesirable weight penalty associated with the adhesive layer that is required for bonding each additional block of foam.

Traditional foam cushions are generally not suitable for mounting directly to the main substructure of an aircraft seat. As such, foam cushions may need to be mounted to a secondary structure which is then mounted to the aircraft seat substructure. For example, a seat pan cushion may need mounting to a diaphragm which provides stiffness to the seat pan cushion and the diaphragm itself is mounted to the aircraft seat substructure. Such secondary structures carry an associated weight penalty which is undesirable in an aircraft seat.

Furthermore, it may be desirable to provide cooling or heating to an aircraft seat to enhance passenger comfort. However, modifying a traditional aircraft seat cushion to provide enhanced cooling or heating for the passenger can be time consuming and costly.

WO 2017/027067 discloses examples of aircraft seats that have been configured to provide enhanced heating or cooling for the passenger. The disclosed aircraft seat assemblies include thermoelectric devices disposed below or within the surfaces of the passenger seat assemblies to define one or more thermal zones. The thermoelectric devices may be configured such that application of a first current having a first polarity causes a temperature of the thermal zone to increase, and application of a second current having a second polarity causes the temperature of the thermal zone to decrease.

The present invention seeks to mitigate the above-mentioned problems.

Summary of the Invention

The present invention provides, according to a first aspect, an aircraft seat comprising a cushion, wherein the cushion is at least partly formed by a resilient monolithic lattice structure.

The aircraft seat may comprise one or more of a seat pan, a back rest, a head rest, and an arm rest. The cushion may be one of a seat pan cushion, a back rest cushion, a head rest cushion, a leg rest cushion, or an arm rest cushion. The aircraft seat may comprise a plurality of cushions at least partly formed by a resilient monolithic lattice structure. In use the cushion may be covered by a removable cushion cover.

The resilient monolithic lattice structure may be formed from a polymer. The polymer may be a thermoplastic such as polyurethane, polyetherimide, or poly(vinylidene difluoride) (PVDF). Alternatively, the resilient monolithic lattice structure may be formed from thermosetting polymers, such as epoxy, phenolic, polyurethane or polyester resins.

Aircraft seat cushions are typically manufactured from foam which is available in various standard grades, an aircraft seat manufacturer seeking to manufacture a cushion having specific elastic properties is therefore limited to the various grades of foam available. Typical examples of foam used in aircraft seats are closed-cell foams of polyurethane or PDVF; these closed-cell foams do not allow for air movement through the foam thereby limiting the heat exchange with the cabin environment. If a cushion having a specific elastic stiffness, or resilience, is required, then the cushion may have to be manufactured from two or more different grades of foam. Thus manufacture of such cushions will require cutting to size two or more pieces of foam and then adhesively bonding the layers of foam together.

The present invention provides a cushion at least partly formed by a monolithic, or“one-piece”, lattice structure. The lattice structure being made up of a multiplicity of repeating unit cell structures. It will be understood by the skilled person that the repeating unit cell structures could take a variety of different forms to achieve the same effect. The unit cell structures may comprise, for example, cuboid structures or three dimensional polygons. The monolithic lattice structure may comprise one or more arrays of regularly sized unit cell structures. Where there are multiple arrays of unit cell structures, those arrays may contain unit cells of different sizes. The lattice structure may be an open-cell lattice cell structure, in other words, the lattice structure may be gas permeable. In this case the elastic stiffness of the lattice structure is dictated by the geometry of the unit cells of the lattice structure.

The lattice architecture may be a closed-cell structure, in other words, the lattice structure may not be gas permeable and may contain pockets of trapped air. In this case the elastic stiffness is dictated by the geometry of the unit cells of the lattice structure and the resilience of the pockets of trapped air.

Such a cushion may be manufactured, for example, by an additive manufacturing process, also known as 3D printing. A benefit of a monolithic lattice structure is that the geometry of the lattice structure is essentially infinitely variable so that a cushion having the exact desired elastic properties can be provided. Cushions having various comfort and firmness requirements can therefore be made by tailoring the geometry of the lattice structure. Such a cushion simplifies the manufacturing process by eliminating the steps of cutting and bonding together foam layers. Standard seat cushions may also require mould tools to shape the various sections of the cushion, which means there are additional non-recurring costs involved in the manufacturing process that are eliminated by the additive manufacturing method. Furthermore, by providing a cushion having the exact desired elastic properties, there is potentially an associated weight saving over an equivalent foam cushion which may be heavier due to the amount of foam required and due to the presence of adhesive. An aircraft seat having a reduced weight is particularly desirable. The monolithic lattice structure may comprise a first region having a first lattice density and a second region having a second lattice density, the second lattice density being different from the first lattice density.

The monolithic lattice structure may comprise a third region having a third lattice density, wherein the third lattice density is different from the first and second lattice densities.

The lattice structure may be formed from a multiplicity of repeating unit cell structures. The lattice density may be controlled by controlling the size of the unit cell structures. The lattice density may be a measure of the number of repeating unit cell structures per unit volume of the lattice structure. Increasing the lattice density may increase the elastic stiffness of the of the lattice structure. Decreasing the lattice density may decrease the elastic stiffness of the lattice structure. The elastic stiffness of the monolithic lattice structure may therefore be controlled by controlling the lattice density of the monolithic lattice structure.

Alternatively, the monolithic lattice structure may comprise a first region formed from a first polymer and a second region formed from a second polymer, the second polymer being different from the first polymer. The monolithic lattice structure may comprise a third region formed from a third polymer, wherein the third polymer is different from the first and second polymers. The elastic stiffness of the first polymer may be different to the elastic stiffness of the second polymer. The elastic stiffness of the third polymer may be different from the elastic stiffness of the first and second polymers. The elastic stiffness of the monolithic lattice structure may therefore be controlled by controlling the type of polymer used to form the monolithic lattice structure.

Aircraft seat cushions having a varying elastic stiffness may be desirable. For example, a seat pan cushion may be constructed with a relatively firm base and a relatively soft seating layer (i.e. the layer that a passenger sits on in use). There may also be one or more intermediate layers. Such cushions are typically manufactured from layers of foam having different densities by cutting the layers of foam to size and then adhesively bonding the layers together.

A cushion comprising a resilient monolithic lattice structure having a first region having a first lattice density and a second region having a second, different lattice density, provides a cushion having regions of differing elastic stiffness in a single one-piece construction. When cushions are constructed from layers of foam bonded together, there is an abrupt change in stiffness and/or density at the interface between the foam layers. However a monolithic lattice structure can provide a cushion having a graduated lattice density and thereby have a graduated stiffness. Furthermore, it is possible to provide complex internal arrangements of lattice density to meet varying stiffness requirements. Such cushions would be too complex, time consuming, and costly to produce from bonding together pieces of foam of differing densities.

The first region may comprise a first layer and the second region may comprise a second layer adjacent the first layer such that the second layer is positioned to be between the first layer and a passenger when the passenger is seated in the aircraft seat. The monolithic lattice structure may comprise a third region having a third lattice density, wherein the third lattice density is different from the first and second lattice densities. The third region may comprises a third layer adjacent the second layer such that the third layer is positioned to be between the second layer and a passenger when the passenger is seated in the aircraft seat.

The cushion may have a rear surface. The cushion may have a front surface. The front surface may be configured to be the surface closest to a passenger when the passenger is sitting in the seat. The first layer may be positioned between the rear surface and the second layer. The second layer may be positioned between the first layer and the front surface. The third layer may be positioned between the second layer and the front surface.

The first lattice density may be greater than the second lattice density and the second lattice density may be greater than the third lattice density.

The cushion may have a first surface and a second, opposite surface. The cushion may comprise a ventilation duct passing through the monolithic lattice structure from one or more openings on the first surface to one or more openings on the second surface. The ventilation duct may be defined by one or more walls that are integrally formed with the cushion so that the ventilation duct forms a conduit through the cushion. For example, where the monolithic lattice structure is an open-celled structure, the ventilation duct may need walls so that air flow through the duct is restricted to within the duct. The ventilation duct may branch within the monolithic lattice structure so that the ventilation duct has more openings on the first surface than on the second surface. The first surface may be a front surface. The second surface may be a rear surface. The front surface may be configured to be the surface closest to a passenger when the passenger is sitting in the seat. The ventilation duct openings may be positioned at any location on the first and second surfaces.

The aircraft seat may comprise an air moving device configured to move air through the ventilation duct between the first surface and the second surface of the cushion. The air moving device may therefore be configured to move air between the surfaces of the cushion to provide cooling or heating to a surface of the cushion configured to be positioned adjacent to a passenger in use.

The aircraft seat may comprise a thermal element configured to heat and/or cool air adjacent to the thermal element, and wherein the air moving device is configured to move the heated or cooled air between the first surface of the cushion and the second surface of the cushion via the ventilation duct. The air moving device may be configured to move air from the first surface to the second surface. The air moving device may be configured to move air from the second surface to the first surface. The air moving device may be a fan. The thermal element may be a heat mat.

The thermal element may be a thermoelectric cooler. Thermoelectric coolers, also known as Peltier plates, are well known. Upon application of a DC electric current to a thermoelectric cooler a first of side of the thermoelectric cooler gets hotter (the heating side) and a second, opposite side of the cooler gets cooler (the cooling side). If the DC current is reversed the heating and cooling sides reverse, so the first side of the thermoelectric cooler becomes the cooling side and the second side of the

thermoelectric cooler becomes the heating side. Therefore in embodiments of the invention comprising a thermoelectric cooler, the thermoelectric cooler may be configurable between a heating mode and cooling mode by reversing the DC current through the thermoelectric cooler. The thermoelectric cooler may comprise a heating side configured to heat air adjacent the heating side and a cooling side configured to cool air adjacent the cooling side

The air moving device may be configured to move the air cooled by the cooling side between the first surface of the cushion and the second surface of the cushion via the ventilation duct. The air moving device may be configured to move the air heated by the heating side of the thermoelectric cooler away from the cushion. Alternatively, the air moving device may be configured to move the air heated by the heating side between the first surface of the cushion and the second surface of the cushion via the ventilation duct. The air moving device may be configured to move the air cooled by the cooling side of the thermoelectric cooler away from the cushion. One of the heating side or cooling side of the thermoelectric cooler may partially define a wall of the ventilation duct within the cushion.

The monolithic lattice structure may comprise an integrally formed outer skin that forms an outer surface of the cushion. The integrally formed outer skin may be configured to provide stiffness to the cushion. When the cushion is a seat pan cushion, the outer skin may form the base of the seat pan cushion and stiffen the base of the seat pan cushion. When the cushion is a back rest cushion, the outer skin may form the rear of the back rest cushion and stiffen the rear of the back rest cushion. When the cushion is a head rest cushion, the outer skin may form the rear of the head rest cushion and stiffen the rear of the head pan cushion.

Providing a cushion with an integrally formed outer skin that provides stiffness to the cushion may eliminate the need for some secondary parts, thereby reducing the complexity and weight of the aircraft seat. For example, by providing a seat pan cushion with an integrally formed skin that provides stiffness to the seat pan cushion may eliminate the need for the diaphragm that the seat pan cushion sits upon in use. This could potentially result in a weight saving of just under half a kilogram per aircraft seat.

The outer skin may comprise fibre reinforcement that is configured to provide stiffness to the cushion. The fibre reinforcement may be carbon fibre. The fibre reinforcement may be glass fibre. The fibre reinforcement may be aramid fibre.

The monolithic lattice structure may comprise an integrally formed mounting portion configured for mounting the cushion to a substructure of the aircraft seat. When the cushion comprises integrally formed skin, the integrally formed mounting portion may be formed in the skin. The monolithic lattice structure may comprise a plurality of integrally formed mounting portions. The mounting portion may comprise a channel configured to engage with and retain a substructure of the aircraft seat. The substructure of the aircraft seat may be a seat frame. When the cushion is part of the seat pan the channel may be configured to engage with and retain a spar tube of the seat substructure. The channel may be configured to snap fit on to a spar tube of the seat substructure. The channel may be configured to slidingly engage with the substructure of the aircraft seat.

The cushion may comprise a thermal conductor embedded within the monolithic lattice structure. The thermal conductor may be configured to conduct heat between a first surface of the cushion and a second surface of the cushion, wherein the first surface of the cushion is configured to be adjacent a passenger when the passenger is sitting in the seat. When the cushion is a seat pan, the thermal conductor may be configured to conduct heat between a seating surface of the seat pan and another surface of the seat pan. The thermal conductor may be configured to conduct to the seating surface of the seat pan. The thermal conductor may be configured to conduct heat away from the seating surface of the seat pan, thereby cooling the seat pan.

The thermal conductor may be a thermally conducting sheet. The thermally conducting sheet may be flexible. The thermally conducting sheet may be a mesh or a plate. The thermally conducting sheet may comprise metals such as aluminium, copper or alloys thereof. The aircraft seat may comprise a thermal element configured to heat or cool the thermal conductor. The thermal element may be a heating or cooling device. The thermal element may comprise a heat mat. The thermal element may comprise a thermoelectric cooler. The thermoelectric cooler may comprise a first side and a second, opposite side. At least part of the first side of the thermoelectric cooler may form part of the second surface of the cushion. The thermal conductor may be connected to the second side of the thermoelectric cooler. The thermoelectric cooler may be configurable so that the first side is a heating side and that the second side is a cooling side. The thermoelectric cooler may be configurable so that the second side is a heating side and that the first side is a cooling side. The first side of the thermoelectric cooler may comprise a heat sink. The thermal element may comprise both a heat mat and a thermoelectric cooler.

The cushion may comprise a second monolithic lattice structure. The first monolithic lattice structure may comprise an integrally formed hinge that is also integrally formed with the second monolithic lattice structure such that the monolithic lattice structures are moveable with respect to one another via the hinge. The integrally formed hinge may have been manufactured at the same time as the monolithic lattice structures by using an additive manufacturing process such that the hinge forms part of monolithic lattice structures.

The monolithic lattice structure may form at least part of a main portion of a head rest cushion. The second monolithic lattice structure may form at least part of a side portion of a head rest cushion. There may be a third monolithic lattice structure that forms a second side portion of the head rest cushion. The side portions of the head rest cushion may be located on either side of the main portion of the head rest cushion.

The monolithic lattice structure may comprise an integrally formed hinge that is also integrally formed with the third monolithic lattice structure such that the monolithic lattice structures are moveable with respect to one another via the hinge.

According to a second aspect, the present invention provides a cushion suitable for use as the cushion of the aircraft seat according to the first aspect of the invention.

According to a third aspect, the present invention provides an aircraft seat unit comprising an aircraft seat according to the first aspect of the invention and a foot rest, wherein the foot rest comprises a cushion at least partly formed by a resilient monolithic lattice structure. The foot rest may be a bed extension.

According to a fourth aspect, the present invention provides a foot rest suitable for use as the foot rest of the third aspect of the invention.

According to a fifth aspect, the present invention provides the use of an additive manufacturing process to manufacture a cushion as defined by the second or third aspects of the invention. Additive manufacturing, or 3D printing, is particularly suited creation of monolithic lattice structures of the type forming the cushion according to the first aspect of the invention. Furthermore, this manufacturing method would allow for replacement cushions to be made anywhere where there is a 3-D printer available. For example, if a defective seat cushion is noticed in flight, a replacement part can be ordered during that flight. The replacement cushion can be printed and made available to install at the destination airport during the regular turn-around time of the aircraft.

It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into any of the other aspects of the present invention.

Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:

Figure 1 shows an aircraft seat according to a first embodiment of the invention;

Figure 2 is a cross-sectional perspective view of the seat pan cushion of the aircraft seat;

Figure 3 shows a unit cell of the monolithic lattice structures which form the seat pan cushion, backrest cushion, head rest cushion, leg rest cushion, and an arm rest cushion of the aircraft seat; Figure 4 shows the seat pan cushion of Figure 2 mounted upon a spar tube structure;

Figure 5 shows the back rest cushion of the aircraft seat;

Figure 6 shows the head rest cushion of the aircraft seat;

Figure 7 shows a seat pan cushion of an aircraft seat according to a second

embodiment of the invention;

Figure 8 is an underside view of the seat pan cushion of Figure 7;

Figure 9 is a cross-sectional view of the seat pan cushion of Figure 7 showing the duct opening and thermoelectric cooler at the lower surface of the seat pan cushion;

Figure 10 shows a seat pan cushion of an aircraft seat according to a third

embodiment of the invention;

Figure 11 is a rear view of the seat pan cushion of Figure 10;

Figure 12 is a cross-sectional view of the seat pan cushion of Figure 10 showing the thermoelectric cooler at the rear edge of the seat pan cushion; and

Figure 13 shows a footrest belonging to an aircraft seat unit according to a fourth embodiment of the invention.

Detailed Description

An aircraft seat 1 according to a first embodiment of the invention is shown in Figure 1. The aircraft seat comprises a seat pan cushion 3, a backrest cushion 5, a head rest cushion 7, a leg rest cushion 9, and an arm rest cushion 10, each of the cushions being mounted to a substructure of the aircraft seat (not shown).

Traditionally, these types of cushion would have been manufactured from a resilient foam material. However, each of the cushions 3, 5, 7, 9, 10 of the aircraft seat 1 of the presently described embodiment of the invention have been manufactured from polyetherimide using an additive manufacturing process. The additive manufacturing, or 3D printing process allows each of the cushions 3, 5, 7, 9, 10 to be manufactured with a resilient monolithic lattice structure which can be seen in detail in Figure 2.

The monolithic lattice structure of each of the cushions 3, 5, 7, 9, 10 is formed by a multiplicity of repeating diamond-shaped unit cell structures. A single unit cell structure 11 is shown in isolation in Figure 3; each cell 11 is formed by four arms 112, each arm 112 having an arm thickness t. The cell 11 has a height Y and a width X.

The elastic stiffness of the lattice structure can be controlled by varying the unit cell height Y and width X and arm thickness t. As the dimensions X and Y decrease, there will be more unit cells per unit volume of the lattice structure (i.e. the lattice density of the resilient monolithic lattice structure increases) and therefore the elastic stiffness of the resilient monolithic lattice structure will increase. Furthermore, the stiffness of each individual unit cell 11 can be increased by increasing the arm thickness t.

The additive manufacturing process used to manufacture the cushions 3, 5, 7, 9, 10 allows the unit cell 11 size to be varied within the lattice so that the cushions 3, 5, 7, 9, 10 can be formed from a single monolithic lattice structure comprising a varying lattice density. As can be seen from Figure 2, the seat pan cushion 3 comprises three layers I, II, III, each layer having a different lattice density. The seat pan cushion 3 of the presently described embodiment of the invention is configured such that the lattice density (and therefore the elastic stiffness) of the lattice structure decreases from the lower surface 31 of the seat pan cushion 3 to the upper surface 32 (seating surface) of the seat pan cushion 3 i.e. the unit cell size of layer I is smaller than the unit cell size of layer III, and layer II comprises an intermediate unit cell size. The seat pan cushion 3 therefore provides a suitable replacement for prior art seat pan cushions which are formed by adhesively bonding together separate layers of foam having different density/elastic stiffness. Using an additive manufacturing process not only simplifies manufacture by eliminating steps of cutting and bonding separate layers, but can also provide a cushion having an open cell structure with better ventilation properties than the foam that is typically used in seat cushions. As such, the resulting cushion is better for passenger comfort than prior art foam-based seat cushions.

The ventilation properties of the seat pan cushion can be further improved by providing a ventilation duct 35 through the seat pan cushion 3, between the upper surface 33 and the lower surface 31, as shown in the cross-sectional view of Figure 2. As can be seen, the duct 35 has a single opening 351 on the lower surface 31 but branches within the seat pan cushion 3 so that the duct has six openings 353 on the upper surface 33. Manufacture of the seat pan cushion 3 with the internally branching duct 35 is facilitated by the additive manufacturing process used to make the seat pan cushion 3. The seat pan cushion 3 can be formed with the duct 35 already in place meaning that subsequent manufacture steps are not needed to make a duct within the seat pan cushion 3. Furthermore, the additive manufacturing process enables cushions having ducts with complex geometries to be manufactured much more easily than by using traditional manufacturing techniques.

A seat pan cushion must typically be mounted to the substructure of the aircraft seat via an intermediate rigid structure which provides stiffness and support to the seat pan cushion in use, and also provides a means of fixing the seat pan cushion to the substructure of the aircraft seat. However, the seat pan cushion 3 of the presently described embodiment of the invention is constructed such that an intermediate rigid structure is not needed. Stiffness is provided to the cushion 3 by the lower surface 31 of the seat pan cushion 3 which is formed from a skin 37 of carbon fibre reinforced polyetherimide. To enable the seat pan cushion 3 to be mounted directly to the aircraft seat substructure, channels 39 are formed in the lower surface 31 of the seat pan cushion 3, as can be seen in Figure 2 and Figure 4, so that the spar tube structure 13 to which the seat pan cushion 3 must be mounted is partially received within the channels 39. The channels 39 have a circular cross section of substantially the same diameter as the spar tubes 131 and are configured to snap-fit on to the spar tubes 131 and retain the spar tubes 131 such that the seat pan cushion 3 can be mounted to the aircraft seat substructure via the spar tubes 131 engaging with the channels 39.

As can be seen from Figure 2, holes 32 can be incorporated into the stiffened skin 37 section during the manufacturing process so that inserts such as, for example, rivnuts 15 can be inserted into the cushion, as shown in Figure 4.

The additive manufacturing process enables the backrest cushion 5 to be manufactured to the necessary dimensions as a single monolithic structure, as can be seen in Figure 5. The general structure of the backrest cushion 5 is substantially the same as the seat pan cushion 3, with an internal monolithic lattice structure comprising a multiplicity of repeating unit cell structures and a rear surface 50 of the back rest 5 being stiffened by a carbon fibre reinforced layer. The back rest also comprises a number of integrated keyways 51 that are integrally formed with the back rest 5 so that the back rest 5 can be mounted to the aircraft seat substructure via a number of complementarily positioned projections located on the aircraft seat substructure.

The headrest cushion 7 of the aircraft seat 1 is shown in isolation in Figure 6. The head rest cushion 7 comprises a main portion 71 that the rear of a passenger’s head can rest against in use and two side portions 73 that are hinge mounted on either side of the main portion 71. The side portions 73, which will be positioned either side of the passenger’s head in use, are moveable with respect to the main portion 71 via the hinges 75 so that the passenger can move the side portions 73 into a position in which the passenger can rest the side of their head against the side portions 73. The additive manufacturing process used to make the head rest cushion 7 enables the head rest cushion 7 to be 3D printed as a single part, with the hinges 75 integrated into the main 71 and side 73 portions. Like the backrest cushion 5 and seat pan cushion 3, the rear surface of the main portion 71 of the head rest 7 also comprises a carbon fibre reinforced skin 77 that provides stiffness to the main portion 71. Furthermore, T- shaped channels 79 are formed in the carbon fibre reinforced skin 77 on the rear surface of the main portion 71 that are configured to receive complementarily shaped formations located on the aircraft seat substructure. The head rest cushion 7 is therefore configured to be mounted upon the aircraft seat substructure by sliding the T-shaped formations (not shown) located on the aircraft seat substructure into the channels 79 located on the head rest cushion 7.

A seat pan cushion 103 belonging to an aircraft seat according to a second embodiment of the invention is shown in Figure 7. The aircraft seat itself is not shown but is substantially the same as the aircraft seat 1 according to the first embodiment of the invention, with the seat pan cushion being the only substantial difference. The seat pan cushion 103 comprises a cooling arrangement that provides cooling air to the upper (seating) surface 133 of the seat pan. The seat pan cushion 103 is manufactured using an additive manufacturing process and is formed with a ventilation duct 135 that passes from the lower surface to the upper surface of the seat pan. As can be seen from Figures 7 and 9, the duct 135 has a single opening 1351 on the lower surface 131 of the seat pan cushion 103 but branches within the seat pan cushion 103 so that the duct has a multiplicity of openings 1353 on the upper surface 133 of the seat pan cushion 103. An inside wall of the duct at the lower surface of the seat pan cushion 103 is partly formed by the cooling side 42 of a thermoelectric cooler 4, or Peltier plate, so that the thermoelectric cooler 4 is configured to cool air within the duct 135. As can be seen from Figures 8 and 9, the seat pan cushion 103 comprises a fan 43 positioned adjacent the opening 1351 at the lower surface 131 of the seat pan cushion 103 such that the fan 43 is partially received in the channel 135 and is thereby able to move air over both the heating side 41 and the cooling side 42 of the thermoelectric cooler 4. Positioned as such, the fan 4 can move air into the duct 135 at the lower surface of the seat pan cushion 103, over cooling side 42 of the thermoelectric cooler 4 which cools the air, and through the duct 135 to the upper surface 133 of the seat pan cushion 103. Furthermore, the fan 4 is also positioned to cool the heating side 41 of the thermoelectric cooler 4 by moving air over and away from the heating side 41 of the thermoelectric cooler 4. As can been seen in Figure 9, a heat sink 45 is positioned on the cooling side 42 of the thermoelectric cooler 4 to enhance the cooling effect of the thermoelectric cooler 4 on the air moving through the duct. A heat sink 46 is also positioned on the heating side 41 of the thermoelectric cooler 4 to enhance the heat dissipation from the heating side 41 of the thermoelectric cooler 4.

A seat pan cushion 203 belonging to an aircraft seat according to a third embodiment of the invention is shown in Figure 10. The aircraft seat itself is not shown but is substantially the same as the aircraft seat 1 according to the first embodiment of the invention, with the seat pan cushion being the only substantial difference. The seat pan cushion 203 comprises a cooling system that cools the upper (seating) surface 233 of the seat pan cushion 203 by moving heat away from the upper surface 233 via a thermally conducting flexible copper mesh 237 located beneath the upper surface 233 of the seat pan cushion 203, as can be seen in Figures 10 and 12. The mesh 237 is connected to the cooling side 142 of a thermoelectric cooler 140 located at the rear edge 2031 of the seat pan cushion 203 (the rear edge 2031 of the seat pan cushion 203 being positioned to the rear of the passenger sitting in the aircraft seat in use). The heating side 141 of the thermoelectric cooler 140 is exposed at the rear edge 2013 of the seat pan cushion 203 so that it can be cooled by air in the vicinity of the rear edge 2013 of the seat pan cushion 203. Furthermore, cooling of the heating side 141 of the thermoelectric cooler 140 is enhanced by a pair of heat sinks 145 that are mounted upon the heating side 141 of the thermoelectric cooler 140, as can be seen in Figure 11 and Figure 12.

As can be seen from Figure 11, the seat pan cushion 203 is formed from a one- piece construction with the mesh 237 being embedded within the seat pan cushion 203. This is achieved by using an additive manufacturing technique to first 3D print a lower portion 2031 of the seat pan cushion 203 before putting the mesh 237, thermoelectric cooler 140, and heat sinks 145 in place on top of the lower portion 2031 of the seat pan cushion 203. Manufacture of the seat pan cushion 203 is then completed by 3D printing an upper portion 2032 of the seat pan cushion on top of the lower portion 2031 and mesh 237.

A foot rest 500 belonging to an aircraft seat unit according to a fourth embodiment of the invention is shown in Figure 13. The seat unit, which is not shown, comprises an aircraft seat substantially identical to the aircraft seat 1 according to the first embodiment of the invention. The footrest 500 comprises a cushion 501 that has been manufactured from polyetherimide using an additive manufacturing process such that the cushion comprises a resilient monolithic lattice structure that is substantially the same as that belonging to the seat pan cushion 3, backrest cushion 5, head rest cushion 7, leg rest cushion 9, and arm rest cushion 10 of the aircraft seat 1 according to the first embodiment of the invention.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

The cooling system of the seat pan cushion 103 according to the second embodiment of the invention is applied to a back rest cushion according to a fourth embodiment of the invention. The back rest cushion comprises a cooling mechanism that provides cooling air to the forward surface of the back rest (i.e. the surface that a passenger’s back rests against in use). The back rest cushion is manufactured using an additive manufacturing process and is formed with a ventilation duct that passes from a rear surface of the back rest cushion to the forward surface of the back rest cushion. The duct has a single opening on the rear surface of the back rest cushion but branches within the back rest cushion so that the duct has a multiplicity of openings on the forward surface of the back rest cushion. An inside wall of the duct at the rear surface of the back rest cushion is partly formed by the cooling side of a

thermoelectric cooler so that the thermoelectric cooler is configured to cool air within the duct. The back rest cushion comprises a fan positioned adjacent the opening of the duct at the rear surface of the back rest cushion which is configured in substantially the same way as the fan of the seat pan cushion according to the second embodiment of the invention so that the fan can move cooling air from the rear surface of the back rest cushion to the forward surface of the back rest cushion.

The cooling system of the seat pan cushion 203 according to the third embodiment of the invention is applied to a back rest cushion according to a fifth embodiment of the invention. The cooling system is configured to cool the forward surface of the back rest (i.e. the surface that a passenger’s back rests against in use) by moving heat away from the forward surface via a thermally conducting copper mesh located beneath the forward surface of the seat back rest cushion. The mesh is connected to the cooling side of a thermoelectric cooler located at a lower edge of the back rest cushion. The heating side of the thermoelectric cooler is exposed at the lower edge of the back rest cushion so that it can be cooled by air in the vicinity of the lower edge of the back rest cushion. Furthermore, cooling of the heating side of the thermoelectric cooler is enhanced by a pair of heat sinks that are mounted upon the heating side of the thermoelectric cooler. The back rest according to the fifth embodiment of the invention is manufactured in substantially the same way as the seat pan cushion according to the third embodiment of the invention.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.