Field of the invention

The present invention relates to a cushion assembly or mattress or the like, particularly a construction comprising two separate foam/air filled sealed cells within a cushion or mattress structure.

Background of the invention

The provision of a cushion or mattress type assembly, e.g. a foam or air cushion, is well known in the art, especially for the purpose of alleviating, or reducing the incidence of, pressure sores. It is often desirable for mattresses or cushions to be supplied for such use in a hospital or healthcare facility on an as-needed basis.

Mattresses or cushions having sealed inflatable segments or cells are well known in the art. These air cells, or in some cases foam filled air cells, are placed as tubes or horizontally adjacent cells within an outer cover. These mattresses or cushions may be connected to an air supply reservoir that provides an air supply to inflate and deflate the multiple cells on an alternating cycle of, for example, 10 minutes. These horizontal cells arrays are then contained in a cover that is typically weave-backed fabric with outer sprayed-on or spread-on plastic coatings. These covers can be removable by opening a zipper at one end of the cover, or by similar means. These systems are typically known as "alternating pressure mattress" systems.

In addition, there are a number of products available which utilise multiple air or foam-air filled cells within a foam outer shell that is then encapsulated within a vapour permeable cover. These are typically known as Self-Adjusting Technology mattresses or SAT mattress systems. These systems again use horizontally placed multiple cells which are connected by tubes to allow air pressure transfer between the multitude of horizontal tubular cells.

As mentioned, the primary purpose of the multitude of open-celled polymeric foam mattresses and support surfaces on the market is to cushion and support a person. These types of mattresses can be uncomfortable for the following reasons; a) The user can sink into the mattress due to the evacuation of the air within the foam when the person/weight is placed on the open celled foam. This is particularly the case with temperature sensitive foam which become softer with body heat. Many people have complained about excessive immersion into standard viscoelastic mattresses. This excessive immersion will cause the viscoelastic foam to "wrap" around the user, i.e. a greater surface area of the user's body is covered by viscoelastic foam. As foam is an insulator it can generate excessive heat which results in discomfort and heat generation which leads to undue perspiration,

b) Mobility while on the mattress - many elderly people have also found that their ability to move or re-position while on a standard Memory foam mattress is restricted due to excessive immersion into the memory foam. This can cause discomfort for people with impaired mobility or musculoskeletal injuries or for elderly people with muscular diseases such as Arthritis, Rheumatism and the like. The present invention overcomes this problem by providing the user with dual sealed foam/air cells within an outer cover. The sealed cells hold the air that is present within the foam and does not allow this air to exhaust, unlike an open mattress without sealed cell interiors. The sealing of the cells ensures air flotation of the person/patient thereby preventing excessive immersion or sinking into the foam. Sealing the foam with a thermoplastic face bonded surface top and bottom also results in improved product longevity.

Many attempts have been made to control and customise the firmness of support surfaces, such as mattresses and cushions. Typically, pressure/shear reducing mattresses are powered by electrically driven motors to pump or vacuum components within or external to the mattress foams.

US Patent No. 2,779,034 to Arpin discloses a spring coil mattress with loose-fitting sealed cover and a vacuum pump for increasing firmness of a mattress by vacuuming air from the mattress. Arpin also discusses an un-bonded core made from "rubber foam" or similar material but this does not specify that the interior of the core is viscoelastic foam or indeed that the interior self-inflating component is used as a depth variation device. Arpin simply uses mechanically pumped negative pressure to spread load in an attempt to reduce interface pressures under the user.

US Pat. No. 3,61 1 ,524 discloses a method of assembling a mattress which involves a complete mattress with an outer skin and a vacuum pump is attached. When vacuum is applied by an electrically powered pump the interior core is compressed and shrunk for ease of transport. When the product is purchased the user opens the valve inside the mattress cover and the mattress returns to full size within the cover. This is a one time, single-use vacuum powered system and is used only to ease packaging and reduce logistics cost. US Pat. No. 6,804,848 (ROSE) teaches a powered layered mattress system which uses pumped air bladders within a composition of layers. Again this is an electrically powered system.

WO01/65978 A3 to GRAEBE discloses a mattresses construction utilising a composite and arrangement of connected air cells. This mattress uses air only cells and resilient material is not incorporated into these cells for auto-inflation. US2003/0208848 A1 (FLICK) discloses a self-adjusting mattress which utilises a series of air bladders with self-sealing one way valves to achieve pressure equilibrium without the involvement of the mattress occupant. These are in an array of linked horizontal un-bonded free- floating elements such as foam or similar are not attached to the relatively rigid vinyl bladders. This again can contribute to unnecessary and unwanted roll effects when laying on the mattress and stability can be compromised with such a construction.

The mattress disclosed in Pat. No. US2003/0208848/A1 is self-adjusting and draws in air through bleed valves when the mattress is not in use. Therefore the mattress must take time to re-adjust and conform each time a user lays on the surface and exerts downward pressure (weight). Over time, the interior of the cells may suffer from Compression set (fatigue in the foam cores) and support levels may be reduced.

US Pat. No. 4,951 ,335 (EADY) discloses another pumped or powered system. This system utilises a pumped or non-pumped core with a piling overlay attached to the top of the air filled layer.

US 2003/0009830 A1 (GIORI) discuss an Adjustable Foam Mattress which is designed to modulate the Hardness (IFD) and density of the mattress foam by sealing them within a hermetically sealed bag or bags with valves for adjustment. The goal of this design is to change the feel of the foam to ensure load dispersion and imitate the feel of heavy viscoelastic foam by utilising standard foam inside a compressed shell. This system also utilises a powered vacuum system to remove air form the sealed bags. The GIORI system claims the use of various densities of foams to achieve even load distribution and feel. No mention is made of the types of outer skin to be used. Skin Maceration in ill patients could therefore be caused by sweating. The system disclosed in GIORI utilises spring- loaded pressure balanced air-intake valves to allow slow self-inflation when weight such as a person is removed from the surface of the mattress.

Referring to the range of well known Self-inflating products in the market, including, but not exclusive to, U.S. Pat. No. 3,872,525 to Lea, GB1526389 to LEA, US,5303,435 to HAAR, US Pat. No.

6,260,222 to Lin. These self-inflating mattresses are typically used in the camping field. They are typically made from non-fire retardant open-celled foams that are sealed in an envelope or envelopes of robust outer fabrics. The outer fabrics are typically designed for durability or as is the case with LIN Pat. No. 6,260,222 for visibility purposes. The foams are designed specifically to allow compression of the mattress to the smallest possible size for efficient storage on a backpack, for example. The outer fabrics are typically designed to be puncture and tear resistant as well as providing long-tern durability when used on open ground over time. These mattresses could not be used in the Home Bedding environment as they are primarily used to insulate against body heat loss when sleeping in the outdoors and the internal foam construction is a highly efficient insulator. Camping Mattresses are therefore unsuitable for use in a home bedding construction for the following reasons: i) Sweating - The insulation factor would be too high and would cause the mattress occupant to sweat excessively.

ii) Range of adjustment - Self-inflation in a camping mattress eliminates the need for a mattress pump which helps the user to reduce pack weight and volume. These mattresses are typically no more than 4-5cm thick and they are not designed to allow sleep surface adjustment or modulation. They simply self-inflate to atmospheric pressure, the valve is closed and the mattress is ready for use.

US 5,282,286 to MACLEISH discusses a self-inflating Cushion that is typically used as a cushion to prevent Decubitus Ulcers in long-term seated patients and wheelchair users. Like GIORI, this system utilises a plurality of resilient elements that are strategically linked within a sealed envelope which has a valve for intake and exhaust of air. The choice of foam elements will be dictated by the expected load range exerted on the cushion when in use. These loads are substantially higher than those experienced in a mattress, as the surface area (seating area) is greatly lessened and pressure within the envelope is increased. (Pressure=Force/Area.). The cushion of MACLEISH also requires the use of a pump system to actively pressurise the cushion. The invention claimed in MACLEISH is a wheelchair cushion with knit/woven backed outer stretch membranes and a plurality of interior foams. EP 2030533 in the name of the present applicant discloses a mattress assembly which comprises an inflatable core comprising an impermeable envelope having a resiliently deformable body within the envelope, a bore/channel within the body and open to the exterior of the body, and a valve permitting airflow into or out of the bore/channel, in order to adjust the level of immersion experienced when a user lies on the mattress assembly.

GB213487 in the name of the present applicant discloses an overlay system for a mattress comprising: i) an overlay comprising a core of a visco-elastic foam material and an external envelope covering the core; and ii) at least one disposable protective cover adapted to fit over the overlay. The current claimed invention is different and novel in that it is not a mattress topper or overlay which is to be placed on top of another mattress. The claimed invention is a full replacement mattress with two sealed foam filled cells and covered with an outer cover to retain the cells.

GB2413488 in the name of the present applicant discloses a futon-type mattress comprising: i). a core of visco-elastic foam material; ii). an air impermeable envelope defining a chamber enclosing the core; and iii). at least one user operable valve for permitting air to flow into and out of the chamber, said futon-type mattress system comprising a plurality of separable articulable mattress sections, each mattress section comprising: i). a core of visco-elastic foam material; ii). an air impermeable envelope defining a chamber enclosing the core; and iii). at least one user operable valve for permitting air to flow into and out of the chamber. The claimed invention is different and novel in that it utilises and relies upon two longitudinal sealed cells which are layered on top of each other on their respective faces to achieve improved shear force reduction. Unlike the product claimed in GB2413488A, the separable cells are not side by side. In the claimed invention the inner cells are layered on top of each other.

Summary of the invention

According to a first aspect of the present invention there is provided a cushion assembly comprising at least two separate inner longitudinal cells which are layered on top of each other, each longitudinal inner cell comprising an air-impermeable envelope enclosing a resilient core of open-cell foam material, the envelope being at least in part secured to the resilient core; and an outer cover enclosing and retaining the at least two inner cores adjacent one another.

Preferably, each inner cell comprises an upper face and a lower face connected by one or more sidewalls, the cells being located with an upper face of one cell contiguous with a lower face of the adjacent cell.

Preferably, one or more of the envelopes comprise two layers of thermoplastic polyurethane.

Preferably, each envelope is substantially air and liquid impermeable, and comprises an inner layer and an outer layer, the inner layer being at least partially attached, e.g. bonded such as heat bonded, to the outer layer and the resilient core so as to provide a plurality of microchannels of an outer surface of at least a top portion of the envelope to enhance the microclimate under the person/patient. The liquid impermeable envelope prevents or at least reduces contamination. A liquid, such as body fluid, water, or the like, cannot pass through the envelope to contaminate the resilient core.

Moreover, the cushion assembly can be cleaned easily and instantly. It will be appreciated that the envelope comprising at least the inner and outer layer of polyurethane material also has an improved air-tightness, even under load and over time.

The cell/envelope is further skin-friendly and provides good comfort to a user, with characteristics similar to air or gel based cushions. In addition, as the cell/envelope is substantially capable of stretching, shear and friction forces on the user's skin and tissues are advantageously reduced. The envelope allows the cushion assembly, in particular the upper cell, to conform very closely to the shape of the user so that an area of contact between the user and the cushion assembly is maximised, which reduces pressure, shear and friction forces experienced by the user when using the cushion assembly, which results from the user's weight. This can further minimise or reduce the incidence of pressure sores or the like. Advantageously, a reinforcing fabric between the inner and outer layers on the bottom face of the base cell/envelope provides good puncture resistance and durability while maintaining the ability to easily clean and/or disinfect the envelope, particularly the outer layer. In a preferred embodiment, the envelope comprises at least one valve capable of controlling airflow into or out of each of the sealed chambers.

Additionally, a second, third or further valve can be comprised. Accordingly, the cells of the cushion assembly can be compacted, e.g. compressed by rolling or folding the cell when at least one valve is open such that air can escape the cell. The compacted state can be retained by closing the valve or valves such that air cannot re-enter the cell. It will be appreciated that compacting the cells, e.g. after use, is advantageous, as the cushion assembly can conveniently be transported or stored.

Preferably, the cells of the cushion assembly can be compressed to an extent that it can

conveniently be transported in a box or bag or the like. Preferably a plurality of valves is provided to increase the flow rate of air into or out of the envelope. For example one or two valves can be provided at each corner/end of the envelope.

Each cell of the cushion assembly can be conveniently decompacted by, for example, allowing air to enter the cells and retaining the air in the cushion, controlled by each valve.

In an embodiment, one or both envelopes are substantially filled by the respective resilient core.

In embodiments, the inner and outer layers have the same or a different polyurethane material. The polyurethane material can be thermoplastic polyurethane.

The reinforcing fabric layer can extend from the base portion along a circumferential portion of the respective cell. In embodiments the reinforcing fabric layer is at least partially attached to the inner layer.

The reinforcing fabric layer can comprise a synthetic or natural material, e.g. a material selected from nylon, polyester, cotton, polyamide or the like. In embodiments, the envelope/inner cells within the cushion or mattress or the like can have polyurethane foam material has a thickness which is in a range of 4 cm to 15 cm when fully auto- inflated.

A recess can be located at a periphery of the resilient core. In embodiments the resilient core is substantially co-extensive with the envelope. Preferably, the foam core substantially fills a void defined by the respective envelope.

At least one handling means or handle can be attached to the envelope. Preferably, the handling means is attached to the outer cover or the envelope such that the cushion is moveable, when in use, e.g. when a user is placed on the cushion assembly. Particularly, the at least one handling means is selected from a strap, knob, carry bag, harness, side handle or the like. For example, the handling means can be attached to the base portion of the envelope such that at least two handles at each side of the cushion are provided. It will be appreciated that this allows lifting of the cushion with or without a user placed on the cushion.

The cushion assem bly can be capable of transform ing between an operating state and a compressed state controlled by the at least one valve on each cell. The washable, sealed envelope of multi-layer high stretch thermoplastic polyurethane, which is at least partially attached to the respective resilient core, provides a complete and durable barrier to contamination and a smooth surface which can easily be cleaned or decontaminated, for example by using antibacterial wipes, standard disinfectants and/or standard cleaning substances. In addition, the pair of cells are contained within an air and liquid impermeable outer cover which is preferably formed from a TPU coated material. This cover provides a further barrier to the ingress of contaminants, thereby improving infection control. The cushion assembly is lightweight (at least in relation to gel-filled cushions), easily transportable, minimises the danger of cross-infection when used successively by two or more users, and which provides a desired level of comfort and benefit while reducing pressure and shear.

As used herein, the term "cushion" or "cushion assembly" refers to a cushion, pillow, mat, mattress, mattress cover, mattress overlay, a supporting structure, such as a support for a body portion or part, e.g. a heel support, a pad-like support for a user, or the like. The cushion assembly can be suitable for use in a domestic, hospital or care home setting on an as-needed basis.

Brief description of the drawings

Figure 1 illustrates an end elevation of a cushion assembly according to an embodiment of the present invention, comprising an upper and lower cell contained within an outer cover;

Figure 2 is a plan view of the finished cushion with the outer cover fully closed and the line of section A-A which represents the section show in Fig. 1 Detailed description of the drawings

Referring now to the drawings, there is illustrated a cushion assembly, generally indicated as 10, which is capable of non-powered inflation and flotation of a person or patient.

The assembly 10 comprises two inflatable cells 1 1 and 12, illustrated in figurel , which is a key aspect of the invention. The pair of cells 1 1 and 12 are layered/stacked one above the other and in face to face engagement, such that the cells 1 1 , 12 can slide relative to one another in order to reduce pressure and shear while at the same time being at least fluid impermeable to provide infection control.

The cells 1 1 and 12 each separately comprise a core or body 14 of resiliently deformable material, preferably foam, most preferably an open-celled foam as hereinafter described. The cells 1 1 , 12 further comprise a gas impermeable envelope 20 surrounding the foam body 14. Finally, the cells 1 1 , 12 comprises at least one valve 22, preferably manually operable, which communicates between an interior and an exterior of the envelope 20, such as to enable air or other gas to be drawn into or expelled from the foam body 14. The cushion assembly 10 further comprises an outer cover 24 surrounding and effectively encasing and retaining the pair of longitudinal cells 1 1 , 12 in position relative to one another. In particular the longitudinal cells 1 1 , 12 are stacked on top of one another, with a user lying on a portion of the outer cover 24 overlying an upper face of the upper cell 1 1 in use. The outer cover 24 may be formed from any suitable material, but is preferably liquid impermeable. The outer cover 24 may for example be formed from a TPU coated material or the like.

The resilient body 14 of the upper cell 1 1 may be formed of a resiliently deformable material, preferably of foam, and in particular a visco-elastic memory foam or latex. A user lies on this upper cell 1 1 and due to the physical properties thereof, enables the cells 1 1 , 12 to suitably conform to the contours of the person lying on the cushion assembly 10. The visco-elastic foam allows a degree of immersion into the cushion assembly 10 while avoiding excessive immersion that can cause the foam to "wrap around" the user. Thus the visco-elastic foam body 14 of the upper cell 1 1 provides increased levels of comfort while maintaining the mobility of a user lying on the cushion assembly 10. With the valve 22 in a closed position, the envelope 20 is entirely sealed or airtight. No powered pumps or other devices are required in order to achieve functionality.

The provision of the air-sealed cell 1 1 ,12 results in less impact of the foam of the body 14 over time, and thus "compression set" or "foam fatigue" is significantly reduced by reducing the mass of the foam within the core 14. In the preferred embodiment illustrated, the envelope 20 is adhered to the upper and lower faces of the foam body 14 of each cell 1 1 , 12. This prevents the phenomenon know as "ballooning" in which pressure resulting from the weight of a person lying on an inflatable mattress caused the mattress to swell up around the person, effectively increasing the immersion of the person and causing immobilisation. This is avoided with the cells 1 1 , 12 of the present invention. However, unlike the upper and lower faces of the body 14, the sidewalls thereof are not adhered to the respective envelope 20, and thus the envelope 20 can move slightly away from the body 14 in the area of the sidewalls. In this way air can pass easily along the sidewalls to reach the valve 22. This ensures that the cells 1 1 , 12 can be quickly deflated to provide a desired immersion level, and allows pressure distribution with reduced shear and friction forces across the entire area of the body 14.

Due to the resilience of the foam body 14, when no weight is present on the cushion assembly 10 and the valves 22 are opened, the cells 1 1 , 12 will automatically re-inflate to original size and shape, and again without the need for pumps or other powered inflating devices. Once the cells 1 1 , 12 have returned to original shape, the valves 22 can be closed and thus the cushion assembly 10 can re-set to full inflation, thereby assuring suitable levels of comfort, body shape adaptation and support while simultaneously reducing pressure and shear by allowing the cells 1 1 and 12 to slide over one another during use. To further improve the comfort level provided by the cushion assembly 10, the envelope 20 of each cell 1 1 , 12 is preferably comprised of a thermoplastic polyurethane (TPU), or at least an outer skin thereof, which reduces the sheer and friction force on the skin tissue of the mattress occupant. The TPU skin of the envelope 20 is designed to imitate the stretch and tensile properties of human skin tissue.

Thus it will be appreciated that by providing the cushion assembly 10 with an upper cell 1 1 and a lower cell 12 stacked on top of one another, it is possible to achieve a preferred and desired level of immersion into the cushion assembly 10, while simultaneously reducing pressure and shear force.