EP2030533B1

EP2030533B1 - A mattress assembly

Info

Publication number: EP2030533B1
Application number: EP08002697A
Authority: EP
Inventors: Patrick Noel Daly
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-02-16
Filing date: 2008-02-13
Publication date: 2011-11-23
Anticipated expiration: 2028-02-13
Also published as: EP2030533A3; ATE534321T1; ES2383423T3; EP2030533A2; DK2030533T3; PT2030533E; PL2030533T3

Abstract

The present invention is concerned with a mattress assembly (10) which comprises an inflatable core comprising an impermeable envelope (20) having a resiliently deformable body (14) within the envelope (20), a network of bores within the body and open to the exterior of the body, and a valve permitting airflow into or out of the network of bores, in order to adjust the level of immersion experienced when a user lies on the mattress assembly.

Description

The present invention relates to mattresses with a non-powered adjustable core, and particularly but not exclusively to mattresses for domestic use.
There are a multitude of open-celled polymeric foam mattresses and support surfaces on the market. The primary purpose of these surfaces is to cushion and support a person. The density and hardness of the foam material within the mattress core will dictate firmness and support levels. For example, a viscoelastic foam layer of 70mm thickness with a density of up to 85Kg/m3 and a hardness of up to 175 Newtons is typically used in a Memory foam mattress. The base support layer may be 100mm thickness of approximately 40Kg/M³ Polyurethane foam with a Hardness of up to 200Newtons.
These types of mattresses can be uncomfortable for the following reasons;

a) The user is not in control of their levels of immersion into the mattress. The weight and shape of the user along with the softness and support of the mattress will dictate the degree of immersion or depth the user will experience when lying on the mattress. 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 an option to adjust the firmness and depth of immersion into the surface of the mattress without the need for pumps, motors and power supply, thereby reducing set-up time, cost of logistics/transport of the mattress and cost to the end-consumer/purchaser of the mattress. It also results in improved product longevity.
Conventional firmness regulating mattresses typically comprise an air filled bladder with powered pump or vacuum supply that is placed between bodies of springs, foams, paddings, waddings, battings and the like. The entire composition of layers is typically encased in suitable external cover.

Background of the Invention

This invention is unique in that it is a non-powered mattress that will allow one or more users to adjust the interior core of the mattress to achieve their preferred and desired level of immersion into the mattress, thereby assuring customised and tailored levels of comfort, body shape adaptation and support.
The inner mattress core is constructed using a layer of open-celled polyurethane foam which is placed within a sealed and bonded envelope of specialised Thermoplastic Polyurethane (TPU) skin material with at least one exhaust port to allow exhaust and intake of air. This exhaust and intake valve is controlled by the person or persons lying on the mattress.
Many attempts have been made to control and customise the firmness of Support Surfaces, such as Mattresses and Cushions. Typically, adjustable and/or firmness regulating mattresses are powered by electrically driven motors to pump or vacuum components within or external to the mattress foams.
US Pat. No. 3,611,524 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 case 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. The invention at hand is a permanently sealed interior self-inflating core which is specifically designed to allow the user infinite re-adjustment without motors or pumps.
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 visco-elastic foam or indeed that the interior self-inflating component is used as a depth variation device. No mention is made of a top comforting layer of memory-foam or other comfort enhancing interface foam. Arpin simply uses mechanically pumped negative pressure to spread load in an attempt to reduce interface pressures under the user. The invention at hand is novel also in that it incorporates stretch Thermoplastic Polyurethane which is bonded to a self-inflating foam core. This provides two key advantages: a) the skin is high stretch and is designed to imitate the stretch and tensile properties of human skin. This provides a greater degree of conformity thereby minimising shear and friction on the skin tissues and musculoskeletal structure of the person on the mattress, which in turn reduces pressure points and enhances circulation, all of which have been shown to contribute to a more comfortable and more effective sleep surface.
EP1 332 697 A3 to the OR group also discloses a similar vacuum pumped system to evacuate a portion of the air within a sealed cover by suction. This is a cumbersome process that will take time and is inconvenient for the user. In addition the system utilises electrical power to supply a vacuum pump. The invention at hand utilises gravitational force (body weight) and a simple exhaust valve to allow the bed occupant to adjust the sleep surface to their preferred immersion, support and comfort levels. This is easily achieved within 5-10 seconds and does not utilise electrical power supply of any type.
US Pat. No. 3,611,524 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. The invention at hand is a permanently sealed interior self-inflating core which is specifically designed to allow the user infinite re-adjustment without motors or pumps.
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. The invention at hand utilises strategically cored foams within the sealed envelope, i.e. the self-inflating core of the claimed invention acts to minimise the roll-effects or buoyancy effects typically associated with standard air mattresses. The interior core of the claimed invention has specifically designed holes/channels which are mechanically cut from the foam in order to enhance self-inflation speed and maximise pressure distribution across the sealed air/foam mattress surface. The foam core also therefore minimises the roll effect as the foam minimises the speed of the displacement of air within the sealed envelope, thereby enhancing comfort and support.
WO01/65978 A3 to GRAEBE discloses a mattresses construction utilising a composite and arrangement of connected air cells. This mattress again uses air only and is not readily or easily adjustable. The interconnected air cells have a pre-determined level of air pumped in at manufacture or at a later stage. The cells in GRAEBE are mechanically pumped with air only and resilient material is not incorporated into these cells for auto-inflation. The claimed invention has an auto-inflating, re-adjustable foam core envelope interior and is infinitely adjustable due to the structure and design of the interior foam core.
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. Also 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 invention at hand is different and novel in that adjustment and support levels are mechanically adjusted by the bed occupant. Also, the interior TPU skins used to make the self-inflating envelope within the mattress are specifically designed to reduce shear and friction force on the skin tissues of the mattress occupant. In addition, the claimed invention uses a permanently sealed self-inflation core and the only way to adjust that is by opening the valve outlet at the side of the mattress.
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. The claimed invention is Instantaneously adjusted and re-edjusted as necessary to find the users ideal comfort setting and that setting is iocked-inlsealed permanently to provide the same comfort and support levels night after night.
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. Unlike EADY, the support surface at hand utilises viscoelastic foam or latex foam as a top comforting surface. Secondly, it does not rely on pumps or motors to achieve degrees of firmness. In addition, the mattress claimed in this application utilises mechanically drilled foam with pre-arranged air channels for airflow efficiency and more directed weight/load dispersion. Finally, the claimed mattress core utilises specialised TPU skin material on the outer of the adjustable core to enhance Comfort, Stretch and conformity by reducing pressure, shear and friction.
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 adjusttment. 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. No mention is made of the effect this skin may have on causing the patient or bed occupant to sweat as a result of being so close or in direct contact with the plastic chambers. Skin Maceration in ill patients could therefore be caused by sweating. No mention is made of the tensile properties of the material used around the sealed foam chambers. 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. The invention at hand does not require vacuum pumps. It does not attempt to change the "feel" of the foam within the core. It simply and effectively allows the user to instantly adjust the mattress core to a closed setting which is retained night after night. It will remain in that sealed position until the valve is manually opened by the user for re-adjustment. Unlike GIORI, the claimed Invention will not self-inflate of its own accord when the person gets off the mattress. Also, the specialised TPU is designed to act as a second skin to imitate the tensile properties of human skin. The inner foam of the sealed envelope has strategically designed cores to allow even dispersions without having to place various densities and grades of foam within one or a multitude of envelopes. GIORI also discusses separate side by side components. These are zipped units that can be attached by mechanical means. These zips could cause unwanted pressure points and discomfort under the skin tissues of the bed occupant, which in the case of a long-term bedridden person, could cause pressure damage to tissues. The invention at hand allows side by side adjustment for a couple, for example. This is achieved by placing two sealed cores within a pre-fabricated foam shell. No mechanical means like zips are required to attach the systems side by side. They are strategically fitted to the foam shell to allow side by side location.
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-tem 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 expected the 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 claimed in MACLEISH also claims the use of a pump system to actively pressurise the cushion. MACLEISH does not claim specialised High/Low Melt TPU membranes. Nor does he claim the cushion is an adjustable surface. In addition, no mention is made of memory foam or latex foam comfort enhancing layers on top of the self-inflatable cushion. The invention claimed in MACLEISH is a Wheelchair cushion with knit/woven backed outer stretch membranes and a plurality of interior foams. The invention claimed in this application is an outer breathable cover, foam shell base with latex or viscoelastic foam top layer and adjustable core mattress, with one or two single sealed envelope/s (Single Bed or Double Bed) incorporating homogenous foam with specially designed cavities within that foam to allow enhanced and adjustable support, comfort and conformity. The type, structure and thickness of the foam which is placed on top of the self-inflating core in the claimed invention is also critically important. This invention typically uses a viscoelastic foam layer(Memory Foam) or a soft latex foam layer on top.
Referring to Broyles, Horace US Patent Number 3 611 524 A . This patent claims the use of a powered/pumped to encase a series of box springs to allow easier and cheaper manufacture and production of a mattress. There is no option for the user or person laying on this mattress to adjust the sleep surface manually or voluntarily. Broyles is not an adjustable mattress, It simply shows a method of more efficient production. Also, Broyles does not use or mention foams of any type within the sealed compression bag and mechanical/electrical pumps are utilised to achieve compression. The invention at hand is designed to provide adjustable immersion and comfort for each unique person/user by allowing the foam filled sealed envelope to be deflated by the person's weight and re-inflated without pumps. i.e. for the internal foam to return to atmospheric pressure.
Referring to COMFORTEX INC. WO 87 06442 A , This mattress uses open foam without any sealed envelope. The hardness and therefore the immersion levels of the person/s laying on the mattress is dictated by the density and hardness of the foams placed under the person. Placement of different and various types, densities, hardnesses of foam in strategic locations is a cumbersome procedure. Therefore, the invention at hand is different in that it allows the person to modulate the hardness and immersion of each unique person through the use of a valve and without the need to open, change and close the mattress each time a new person lays on the mattress.
Referring to HOMOMENSUA, EP 1 329 177A , This mattress uses open foam without any sealed envelope. The hardness and therefore the immersion levels of the person/s laying on the mattress is dictated by the density and hardness of the foams placed under the person. Therefore, the invention at hand is different in that it allows the person to modulate the hardness and immersion of each unique person through the use of a valve.
Referring to DALY PATRICK NOEL, GB2413488 , this product discloses a futon style self-inflating mattress for easy storage and compression. It also discloses specialised covering layers for both integration into the envelope coating fabrics and the outer covers used. The purpose of the invention in DAILY GB241 3488 is to provide additional space saving and storage efficiency. In addition DALY provides for breathable covers and a plurality of bores within the foam inside the sealed envelope. Additionally, DALY GB2413488 specifies that the space-saving futon mattress can be supplied in sections if necessary. Finally, the materials used in DALY GB2413488 are different in specification and technical detail to the materials used in the invention claimed in this application. The differences between DALLY 2413488 and the invention at hand are as follows:

a) The invention at hand aims to provide an adjustable sleep surface.
b) The invention at hand does not use bores or holes in the foam
c) The invention at hand uses multi-laminate Thermoplastic Polyurethane of a thickness between 80 and 200 microns to achieve the required performance.
d) The invention at hand does not rely on one specific type of foam to achieve the adjustment and comfort features required. It must simply be an open-celled foam
e) The invention at hand utilises an air channel around the periphery of the outer foam and inside the envelope seal to allow fluid communication with the outer air and therefore provide a faster air intake and exhaust for optimum adjustment response.

The invention is a mattress assembly as defined in claim 1.
Preferably, the cavity is open to an exterior of the body.
Preferably, the assembly further comprises at least one valve communicating between an interior and an exterior of the envelope.
Preferably, the body is comprised of foam.
Preferably, the body is comprised of an open celled polyurethane foam.
Preferably, the envelope is fixed to at least one of the upper or lower faces.
Preferably, the assembly further comprises a base defining a well in which the core is removably locatable.
Preferably, the base comprises a base support structure and side and end walls surrounding and extending upwardly at marginal edges of the base support structure, thereby to define a well in which the core is removably locatable.
Preferably, the assembly comprises a top layer of open cell foam enclosing the core within the well.
Preferably, the top layer comprises a viscoelastic or latex foam.
Preferably, the assembly comprises an inner cover removably locatable about the combined core and base.
Preferably, the assembly comprises an outer cover removably locatable about the combined core and base or about the inner cover.
Preferably the envelope comprises a thermoplastic polyurethane outer skin.
Preferably, the envelope is not adhered to the sidewall of the body, in order to allow unhindered air flow around the periphery of the inside of the envelope.

Brief description of the drawings

For a better understanding of the invention, and to show how the same may be carried into effect, reference will be made by way of example only to the following drawings in which:

Figure 1 is a view of an existing typical memory foam mattress core structure
Figure 2 is a view of the uncontrolled immersion and bottoming out a person experiences when they lay on a standard memory foam mattress.
Figure 3 is a sectioned side elevation of a mattress assembly according to the present invention.
Figure 4 is a section side elevation of a core forming part of the mattress illustrated in figure 3.
Figure 5 illustrates an end elevation of the core of figure 4.
Figure 6 illustrates a plan view of the core illustrated in figures 4 and 5,
Figure 7 illustrates a plan view of the mattress assembly illustrated in figure 3, in which a pair of the cores of figure 3 are located side by side.

Detailed description of the drawings

Referring now to the company drawings, there is illustrated a mattress assembly, generally indicated as 10, which is capable of non-powered inflation/deflation in order to adjust the level of immersion experienced when a user lies on the mattress assembly 10. The assembly 10 comprises an inflatable core 12, illustrated separately in figures 4 and 5, which is a key aspect of the invention. The core 12 comprises a body 14 of resiliently deformable material, preferably foam, as hereinafter described.
Referring back to figure 3, the assembly 10, in a preferred arrangement, further comprises a base 24, which in use retains and supports the core 12 as hereinafter described. In particular, the base 24 comprises upstanding side walls 26 and end walls 28 within which is defined a cavity or well 30 which is shaped and dimensioned to removably retain the core 12 therein, or a pair of the cores 12 in side by side relationship as in figure 7. The assembly 10 preferably comprises a top layer 32, preferably of foam, and in particular a viscoelastic memory foam or latex, which is located over the core 12 such as to enclose same within the well 30. A user lies on this top layer 32, and due to the physical properties thereof, enables the mattress assembly 10 to suitably conform to the contours of the person lying on the mattress assembly 10.
In the use the core 12 is located within the cavity or well 30, and the inner cover 34 secured over the core 12 in order to seal the core 12 within the well 30. An inner cover 34 is then preferably removably located about the combined base 24 and core 12, as illustrated in figure 3. This inner cover 34 is preferably formed from a material such as breathable cotton gauze, although for specialist requirements may be formed from a material such as a breathable polyurethane. Such a material may be chosen for users who have dust allergies, asthma, or other respiratory conditions. An outer cover 36, whose primary purpose is to provide an aesthetic appeal to the assembly 10, is then preferably located about the inner cover 34, in order to complete the mattress assembly 10, again as illustrated in figure 3. Both the inner cover 34 and outer cover 36 may be removed for cleaning/replacement, or for any other reason.
With the core 12 within the well 30 of the base 24, the valve 22 is dimensioned to project through the respective sidewall 26 so as to be accessible from the exterior of the base 24. In this way the valve 22 may be operated by a user when lying on the mattress assembly 10. With the valve 22 in a closed position, the envelope 20 is entirely sealed or airtight. When the valve 22 is opened, air is capable of entering and being expelled from the interior of the foam body 14. Thus if a user lies on the mattress assembly 10 and opens the valve 22, the weight of the user's body will compress the foam body 14, so expelling air from the valve 22. As a result by lying on the mattress assembly 10 and opening the value 22, the level of immersion within the mattress assembly 10 can be tuned to a desired level. Once that level has been reached, the valve 22 is simply closed. No powered pumps or other devices are required in order to achieve this functionality. Additionally, the user may not wish to adjust the mattress core and may find it perfectly comfortable without adjustment.
In the preferred embodiment illustrated, the envelope 20 is adhered to the upper and lower faces of the foam body 14. 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 immobilization. This is avoided with the core 12 of the present invention. However, unlike the upper and lower faces of the body 14, the sidewalls thereof are not adhered to the 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 through and along the sidewalls to reach the valve 22. This ensures that the core 12 can be quickly deflated to provide a desired immersion level, and allows pressure equalisation across the entire area of the body 14.
Due to the resilience of the foam body 14, when no weight is present on the mattress assembly 10 and the valve 22 is opened, the core 12 will automatically re-inflate to its original size and shape, and again without the need for pumps or other powered inflating devices.
Once the core 12 has returned to its original shape, the valve 22 can be closed and thus the mattress assembly 10 can be quickly and easily re-set to full firmness, and adapted for new users, or simply for differing requirements of the same user. The mattress assembly 10 therefore provides a user with the ability to achieve their preferred and desired level of immersion into the mattress assembly 10, thereby assuring customised and tailored levels of comfort, body shape adaptation and support.
To further improve the comfort, level provided by the mattress assembly 10, the envelope 20 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 imitates the stretch and tensile properties of human skin tissue.
Furthermore, the top layer 32 is preferably formed from a viscoelastic "memory foam" or latex foam, and in the preferred embodiment illustrated is approximately 5cm in thickness. This top layer 32 may for example have a density of up to 85kg/m³ cube and hardness of between 70 and 130 Newtons. The top layer 32 allows a degree of immersion into the mattress assembly 10 while avoiding excessive immersion which can cause the foam to "wrap around" the user. Thus the top layer 32 provides increased levels of comfort while maintaining the mobility of a user lying on the mattress assembly 10.
Referring to figure 7, it can be seen that the mattress assembly 10 may comprise two (or more) of the inflatable cores 12 in side by side relationship, such as to form a "double bed". This will allow each side of the bed to be customised to suit the requirements of the individuals sharing the bed.
It will therefore be appreciated that the mattress assembly 10 of the present invention provides non-powered adjustability in order to vary the firmness and depth of immersion into the surface of the mattress assembly 10.

Claims

A mattress assembly comprising an inflatable core (12) comprising an impermeable envelope (20), a resiliently deformable body (14) within the envelope (20); and at least one cavity (16) within the body (14) whereby the body (14) is substantially rectangular parallel piped in shape, having an upper face and a lower face and a sidewall extending therebetween and the envelope (20) is fixed to at least one of the upper or lower faces, characterized in that the envelope (20) is not adhered to the sidewall of the body (14) in order to allow unhindered air flow around the periphery of the inside of the envelope (20).
A mattress assembly according to claim 1 in which the cavity (16) is open to an exterior of the body (14).
A mattress assembly according to any preceding claim further comprising at least one valve (22) communicating between an interior and an exterior of the envelope (20).
A mattress assembly according to any preceding claim in which the body (14) is comprised of foam.
A mattress assembly according to any preceding claim in which the body (14) is comprised of an open celled polyurethane foam.
A mattress assembly according to any preceding claim further comprising a base (24) defining a well (30) in which the core (12) is removably locatable.
A mattress assembly according to claim 8 in which the base (24) comprises a base support structure and side and end walls surrounding and extending upwardly at marginal edges of the base support structure, thereby to define a well in which the core is removably locatable.
A mattress assembly according to claim 9 comprising a top layer (32) of open cell foam enclosing the core within the well (30).
A mattress assembly according to claim 10 in which the top layer (32) comprises a viscoelastic or latex foam.
A mattress assembly according to claims 10 and 11 further comprising an inner cover (32) removably locatable about the combined core (12) and base (24).
A mattress assembly according to any preceding claim comprising an outer cover (36) of breathable material removably locatable about the combined core (12) and base (24) or about the inner cover (32).
A mattress assembly according to any preceding claim in which the envelope (20) comprises a thermoplastic polyurethane outer skin.