Abstract:
A cushion assembly has first and second foam layers that are fixedly connected to each other so as to be contiguous. The cushion assembly also includes a fire-retardant covering and finds particular use as the seat base of a vehicle seat, especially an aircraft seat.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a cushion assembly. In particular, the present invention relates to a seat cushion assembly for a vehicle. 
         [0002]    Cushions or cushion assemblies are known to be provided for forming a part of a seat, in particular the seat base of a vehicle seat. Cushion assemblies are also known to be provided for forming at least a part of a seat back support. 
         [0003]    There are certain qualities that are desirable for a cushion assembly intended to form a part of a seat, in particular a vehicle seat, to possess. For example, a cushion assembly that is intended to form a base, or a seating portion, of a seat, will ideally provide both comfort and support to a person occupying the seat. Comfort is a particularly relevant factor for a vehicle seat, such as an aircraft seat, which may be occupied by a person for a significant duration of time. Known aircraft seats, for example, provide a seat cushion, or a seat cushion assembly, having a rigid support frame for supporting the seat cushion. The disadvantage of such a frame is that they are usually relatively heavy, which is undesirable in a vehicle such as an aircraft. 
         [0004]    Thus, rather than using support frames, it is possible for the appropriate support to be provided by the seat material. For example, seat cushions that utilize a foam material are known. The use of foam imparts a number of beneficial properties such as comfort, softness, even support, moldability, and shape memory. Different foams have different densities and varying degrees of firmness, shape-memory, and rigidity. 
         [0005]    Seats cushions intended for use in aircrafts preferably possess other qualities or characteristics that are particularly appropriate for the aircraft environment. For example, they may preferably exhibit a high degree of energy absorption for impact resistance and may also have the ability to float in water. Additionally, fire retardant aspects may be integrated into aircraft seats to reduce the spread of a potential fire. 
         [0006]    Although a number of seat cushion assemblies are known, there is still a need to improve the previously proposed designs, in particular to provide an improved cushion assembly for a vehicle seat. Embodiments of the present invention seek to provide an improved cushion assembly for a vehicle seat, in particular for an aircraft seating system. 
       SUMMARY OF THE INVENTION 
       [0007]    According to a first aspect of the present invention, there is provided a cushion assembly for an aircraft seat including a first foam layer and a second foam layer; wherein the first foam layer is secured to the second foam layer forming a cushion element, the cushion assembly further including a fire-retardant material that extends around the outer surface of the cushion element. 
         [0008]    Thus, the first foam layer is preferably fixedly secured to the second foam layer in a manner that is relatively permanent, i.e., it is difficult or impossible to separate the first and second foam layers without causing damage to one or both of the foam layers. The first foam layer may, for example, be secured to the second foam layer by means of an adhesive or glue such as, for example, a single part water based adhesive that securely bonds the first foam layer to the second foam layer. 
         [0009]    It will be appreciated that according to particular embodiments of the present invention, it is not intended for the first and second foam layers to be detachable. This offers the opportunity for improved quality control and/or improved durability of the cushion element. Moreover, the provision of a cushion element in which the first and second foam layers are fixedly secured to each other and, therefore, are formed and provided as a single unit, advantageously allows for the individual characteristics of the first and second foam layers to be carefully selected so as to be complementary and/or to fulfill different criteria. 
         [0010]    Thus, for example, the first foam layer may exhibit a higher firmness and/or exhibit a higher compressive strength and/or be more rigid and/or more lightweight than the second foam layer. Preferably, the properties of the first foam layer are selected to provide a high level of firmness or rigid support for the seat cushion assembly, without adding significant weight to the assembly. The first foam layer may preferably be readily moldable to a required shape and size and may also beneficially include fire-retardant properties. The molded density of the first foam layer may preferably be between 30 g/liter and 65 g/liter. More preferably the molded density of the first foam layer is between 45 g/liter and 60 g/liter. The firmness of the first foam layer is preferably at least 200 N. The density and/or firmness of the first foam layer may be selected and/or varied to suit the particular requirements and the intended use of the cushion assembly. An example of a suitable material for the first foam layer is expanded polypropylene. 
         [0011]    The second foam layer, which is provided above the first foam layer when the cushion assembly is provided in normal use, will preferably exhibit a greater softness and/or exhibit a lower compressive strength and/or be less rigid and/or more shape adaptive than the first foam layer. Thus, the properties of the second foam layer are selected to provide a softer, more comfortable layer positioned above the more rigid supportive first foam layer. The molded density of the second foam layer may preferably be between 40 g/liter and 65 g/liter. The firmness of the second foam layer is preferably between 100 N and 400 N. The density and/or firmness of the second foam layer may be selected and/or varied to suit the particular requirements and the intended use of the cushion assembly. An example of a suitable material for the first foam layer is polyurethane or graphite filled polyurethane or combustion modified high resilience polyurethane. 
         [0012]    The first foam layer is provided beneath or below the second foam layer such that the upper surface of the first foam layer is secured to the lower surface of the second foam layer. Preferably the entirety of the upper surface of the first foam layer is secured to a corresponding surface area of the lower surface of the second foam layer, or vice versa. Preferably, the upper surface of the first foam layer is contiguous and/or conformal with the lower surface of the second foam layer. This continuity of connection between the first and second foam layers is beneficial in that it ensures a consistent and/or homogenous support for a user. According to particular embodiments, the absence of any pockets or cavities between the first and second foam layers results a superior cushion in terms of comfort and, moreover, in term of ease of manufacture. Indeed, the simple design provided by embodiments of the present invention enables the cushion assembly to manufactured easily and efficiently, leading to improved assembly times. The consolidation of seat assembly components results in an elegant and efficient design with reduced total seat part count. 
         [0013]    Preferably, the fire-retardant material is provided around the cushion element so as to substantially extend around the outer surface of the cushion element. In this sense, the cushion assembly is wrapped in a fire-retardant material. The fire retardant material preferably extends around the entire surface of the cushion element, thereby providing enhanced fire-protection properties as compared to cushion assemblies that merely provide fire-resistant elements as part of a cushion assembly. The fire retardant material may, for example, include a fire-block fabric. 
         [0014]    The cushion assembly may further include a cover, or trim, that may be selected for aesthetic reasons and may be any material, such as, e.g., leather or a synthetic material. The cover extends around at least a part of the outer surface of the fire retardant material. 
         [0015]    Thus, the cushion assembly provides a seat surface adapted to receive a user. Preferably, one or both of the foam layers may be ergonomically shaped and/or sized and/or configured to provide a seating surface upon which a user may sit. 
         [0016]    According to a second aspect of the present invention, there is provided a method of manufacturing a seat cushion assembly including: forming a first foam layer; forming a second foam layer; and connecting the first and second foam layers such that the first foam layer underlies the second foam layer and wherein the upper surface of the first foam layer is secured to the lower surface of the second foam layer. 
         [0017]    The method preferably involves molding the first foam layer so as to have a desired shape and/or geometry. The first foam layers may include in-mold features which are added as part of the manufacturing/molding process. The first foam layer is preferably rigid and, therefore, tends to maintains the shape formed during the molding process. The second foam layer is preferably not rigid and, therefore, the lower surface of the second foam layer generally conforms to the shape of the upper surface of the first foam layer, while the upper surface of the second foam layer tends to conform to the shape of the buttocks and legs of a user. 
         [0018]    According to a third aspect of the present invention there is provided a seat having a cushion assembly according to the first aspect. 
         [0019]    According to a fourth aspect of the present invention there is provided a vehicle, vessel, and/or aircraft having a seat according to the third aspect. 
         [0020]    Embodiments of the present invention advantageously provide a cushion assembly having superior support and/or comfort to known cushion assemblies, enabling a cushion element to be constructed from first and second foam layers selected to achieve a particular combination of characteristics. Moreover, as a consequence of the first and second foam layers being fixedly connected so as to hinder replacement of one or the other of the foam layers alone, a greater level of quality control can be achieved. This is particularly advantageous in the context of a vehicle seat or aircraft seat, where it is often necessary for the seat manufacture to provide a warranty for the seat product. Moreover, the arrangement of the first and second foam layers so as to be contiguous or conformal with each other ensures a more even, and therefore more comfortable, seating surface for a user. The simple design also benefits from easy manufacture and a simplified assembly process. 
         [0021]    Features of any given aspect may be combined with the features of any other aspect, and the various features described herein may be implemented in any combination in a given embodiment. 
         [0022]    Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a sectional elevational view showing a seat cushion assembly according to an exemplary embodiment of the present invention. 
           [0024]      FIG. 2 a    is a perspective view showing a row of aircraft seats each including a cushion assembly according to another exemplary embodiment of the present invention. 
           [0025]      FIG. 2 b    is a series of perspective views schematically showing the manner of assembly of one of the cushion assemblies shown in  FIG. 2   a.    
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]      FIG. 1  shows a cushion assembly  10  according to an embodiment of the present invention. Although in this example the cushion assembly  10  forms a seat base, it will be appreciated that the cushion assembly  10  may form, e.g., the back of a seat. 
         [0027]    The cushion assembly  10  shown in  FIG. 1  includes a first foam layer  1  and a second foam layer  2 . An upper surface of the first foam layer  1  is secured to a lower surface of the second foam layer  2  by means of an adhesive layer  3  to form a cushion element  4 . The cushion element  4  is entirely covered in a fire-block fabric  5  that entirely wraps around the outer surface of the cushion element. A lightweight leather trim or cover  6  is also provided that extends around an upper surface of the cushion assembly  10  in normal use, as well as around side edges thereof, if desired. 
         [0028]    The first foam layer is molded such the geometry of the first foam layer  1  and/or the resulting cushion assembly  10  varies. Specifically, it can be seen from  FIG. 1 , which shows a cross section through the cushion assembly  10 , that the thickness of the cushion assembly  10  varies. Thus, the upper surface of the first foam layer  1  exhibits a sloping portion  7  such that the thickness of the first foam layer  1  varies from a first thickness t 1  to a second thickness t 2 . The thicker section t 2  of the cushion assembly  10  is intended to be located at or near the back of the seat in use, thereby providing a more ergonomic profile and greater degree of support to the lumber region of a user. Furthermore, the lower surface of the first foam layer  1  is also shaped so as to allow the cushion to be received on a pair of seat spars  8 . 
         [0029]    The first foam layer  1  is intended to provide support to a user in use and includes expanded polypropylene having inherent fire resistive properties, a molded density of around 55 g/liter, and a firmness of greater than 200 N. It will be appreciated that “support” refers to the ability of the foam to “push back” against weight and prevent the foam from changing shape. The second foam layer  2  includes combustion modified high resilience polyurethane having a molded density of 65 g/liter and a firmness of between 100 N and 400 N. It will be appreciated that “firmness” refers to a measurement of the surface feel of the foam and is a measure of the force expressed in Newtons required to compress a test piece to a specified percentage of its originally thickness. Both support and firmness affect the resulting comfort of the cushion, and it is advantageous for the properties of the two layers  1  and  2  to be selected to provide desired levels of both of these quantities. 
         [0030]      FIG. 2 a    shows a row of aircraft seats  21  each including a cushion assembly  20  according to another example embodiment of the present invention. A schematic view of one of the cushion assemblies  20  is shown in  FIG. 2 b    and includes a first foam layer  22  and a second foam layer  23 . An upper surface of the first foam layer  22  is secured to a lower surface of the second foam layer  2  by means of an adhesive layer to form a cushion element. This cushion element is entirely covered in a fire-block fabric to form a fire-blocked cushion element  24 . A lightweight leather trim or cover is also provided to the cushion assembly  25 . 
         [0031]    It should be noted that the above-mentioned embodiments illustrate, rather than limit, the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single feature or other unit may fulfill the functions of several units recited in the claims. Any reference signs in the claims shall not be construed so as to limit their scope. 
         [0032]    The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.