GB2244000A - Mattress - Google Patents

Abstract

A mattress comprising first, second and third layers of plastics foam (12, 14, 16) laminated together to form a rectangular block, the second, intermediate layer (14) being made of an open cell plastics foam of density 33-40 kg/m<3> and hardness 100-150 N, and both of the outer first and third layers (12, 16) being made of an open cell plastics foam of density 27-32 kg/m<3> and hardness 70-120N, the block being enclosed fully in a cover (18) made of a stretch fabric. A simpler, non-reversible embodiment can comprise first and second layers of plastics foam laminated together to form a rectangular block, the first layer consisting of an open cell plastics foam of density 33-40 kg/m<3> and hardness 100-150 Newtons, and the second layer consisting of an open cell plastics foam of density 27-32 kg/m<3> and hardness 70-120N, the block being enclosed fully in a cover made of a stretch fabric. The foam material is preferably a combustion modified polyurethane foam. The cover (18) is preferably a weft knitted nylon fabric laminated to a layer of polyurethane film. The foam layers may be connected together using a cured neoprene adhesive. <IMAGE>

Description

DESCRIPTION MATTRESS The present invention is concerned with mattresses for beds and in particular with mattresses which are especially suited to use on hospital beds.

In order to minimise the occurrence of pressure sores and maceration of the skin in hospitalised patients, it is well known that the mattress on which a patient lies should be designed so that the pressure exerted on any particular part of the patient by the mattress should be below that at which body tissue infarction occurs, namely about 35 mmHg. If the pressure is above this value by whatever amount, then the blood supply to the tissue in that area can be cut-off sufficiently to cause possibly irreversible necrobiosis or necrosis of the skin and underlying tissue.

A typical National Health Service bed provided for general use exerts a pressure of between 90 120 mmHg and so is likely to cause problems if used by patients with low or negligible mobility who are unable to keep adjusting their position and reducing the pressure at vulnerable points on their bodies. Even so, patients with reasonable or normal mobility can still experience great discomfort and substantial pressure sores if they are obliged to use such mattress for more than a short period.

In the case of patients who have only a small or zero mobility, such as for example old atients who have suffered falls, it is therefore essential to provide a special low pressure mattress if such problems are to be avoided or minimised. The problem is made even more acute where the patient is suffering from any of the multitude of conditions which result in the patient's blood pressure being much lower than normal.

Attempts have been made previously to design a low pressure mattress by using a laminated foam construction what has internal pressure relieving channels. The top layers of such known mattresses are designed to be compliant so as to provide cushioning for bony prominences where pressure loading peaks are experienced. Firmer inner layers are provided in selected areas of the mattress to give extra support in these areas, e.g. for supporting the pelvic regions when the patient is sitting up. The mattress is covered by a removable cover made of a flame retardant stretch cover made from a knitted terry fabric which provides a degree of stretch to enable the cover to follow deformations of the mattress surface caused by the patient.

Such known mattresses, whilst certainly providing improved performances compared to the conventional NHS mattress mentioned above, still have a number of problems and disadvantages associated with them. Firstly, the construction of these mattresses is relatively complex and involves at least four layers which are all of different shape and size, and some of which need to be formed with grooves and/or cut-out regions to provide the above-mentioned pressure relieving channels. This results in a correspondingly complex and costly constructional process such that the resulting mattress becomes too expensive for general acceptance. Secondly, these known mattresses are built up on a foam base which forms respective channel-like supports at the two longitudinal ends of the mattress. As a result, the mattress can only be used one way up, i.e. it cannot be used upside down.Thirdly, the known mattresses use butadiene adhesives to attach together the various layers of foam, of which there are at least four. Such adhesives have the characteristic of remaining tacky, so that in use the various foam layers tend to move one relative to another whereby with time the mattress loses it shape and ability to maintain performance. Fourthly, the cover in these known mattresses is waterproofed by the application of a plastics seal using a doctor blade technique. This inevitably results in a number of tiny holes being left in the seal through which liquid can pass so that, in use, it is found that the waterproofing is unreliable. As a result the cover must be made removable to that it can be changed regularly.Fifthly, because of the particular choice, combination and arrangement of the foam materials actually used in these known mattresses, the required performance of maintaining pressure below 35 mmHg at all points on the patient is not actually achieved in practice.

It is an object of the present invention to provide a mattress which avoids or at least substantially mitigates the problems and disadvantages of known mattresses and enables the pressure to which all parts of a patient's body are subjected to be maintained below 35 mmHg for all except extreme cases.

In accordance with a first aspect of the present invention, there is provided a mattress comprising first and second layers of plastics foam laminated together to form a rectangular block, the first layer consisting of an open cell plastics foam of density lying in the range 33-40 kg/m3 and hardness in the range 100-150 Newtons, and the second layer consisting of an open cell plastics foam of density lying in the range 27-32 kg/m3 and hardness in the range 70-120 N, the block being enclosed fully in a cover made of a stretch fabric.

In accordance with a second aspect of the present invention, there is provided a mattress comprising first, second and third layers of plastics foam laminated together to form a rectangular block, the second, intermediate layer being made of an open cell plastics foam of density lying in the range 33-4C kg/m3 and hardness in the range 100-150 N, and bot9 of the outer first and third layers being made of an open cell plastics foam of density lying in the range 27-32 kg/m3 and hardness in the range 70-120 N, the block being enclosed fully in a cover made of a stretch fabric.

In a preferred embodiment, the open cell plastics material is a combustion modified polyurethane foam.

Preferably, the thickness of the intermediate layer is not less than 2" (5.08 cms).

Preferably, the thickness of the first and third layers is not less than 1" (2.54 cms) and not greater than 11/2" (3.81 cms).

Preferably, the overall thickness of the block is not less than 5" (12.70 cms) and not more than 7" (17.78 cms).

The transverse and longitudinal dimensions of the block are freely selectable to suit the mattress dimensions required.

The stretch fabric material of the cover is preferably a weft knitted nylon fabric which is laminated to a layer of polyurethane film. Advantageously, the polyurethane forming said film is ether-based.

Advantageously, the various layers of the open cell plastics material are connected together using a neoprene adhesive.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic perspective view of one embodiment of a mattress in accordance with the present invention, with the outer cover partially cut-away at one end; and Fig. 2 is a sectional view through the inner foam core of the mattress of Fig. 1.

Referring to the drawings, the illustrated mattress comprises an inner foam core 10 consisting of three laminated layers 12, 14, 16 of foamed plastics permanently connected together using a cured neoprene adhesive at the interfaces to form a regular rectangular cuboidal block. The middle layer 14 is made of an open cell, combustion modified, polyurethane foam having a density of not less than 33kg/m3 and not more than 40 kg/m3, and a hardness of not less than 100 N (Newtons) and not more than 150 N. The outer layers 12, 16 are both made of an open cell, combustion modified, polyurethane foam having a density of not less than 27 kg/m3 and not greater than 32 kg/m3, and a hardness of not less than 70 N and not more than 120 N.In a preferred embodiment, the middle layer has a density of about 35 kg/m3 and a hardness of about 130 N and both outer layers 12, 16 have a density of about 30 kg/m3 and a hardness of about 100 N. Where both layers 12, 16 are the same, it will be appreciated that the mattress can be turned over and presents identical characteristics in both orientations.

The inner core 10 is completely enclosed by a permanent cover 18 (see Fig. 1) made of a stretch fabric which is weft knitted from textured nylon. The resulting nylon fabric is rendered completely liquid proof by laminating it between heated calender rollers with a layer of polyurethane film placed on one side of the nylon fabric. The polyurethane used for this film is ether-based to give high flexibility and elasticity and resistance to fluids. Because of the efficient and reliable liquid proofing thereby achieved, the cover can remain on the mattress permanently so that it does not require frequent changing as in the known mattresses described hereinbefore.

Although the cover 18 formed in this manner is completely liquid proof, it remains nevertheless sufficiently permeable to vapours to enable it, and the body parts in contact with it, to "breath" and thereby prevent condensation of body fluids in these contact regions.

The thickness of the central layer 14 must be more than 2" (5.08 cms) and is preferably about 3" (7.62 cms). The thickness of each outer layer 12, 16 lies between 1-11/2" (2.54-3.81cms) and is preferably about 1" (2.54 cms). In practice, it is found that the overall thickness of the core 10 should be not less than 5" (12.70 cms) and not greater than 7" (17.78 cms).

It has been discovered in practice that a mattress constructed in the aforegoing manner exhibits an interface pressure between itself and all parts of the patient which is less than the critical value of 35 mmHg, except in the most extreme cases, e.g. of unusually high weight/size ratio. The mattress is usable on both sides so that it has an extended life expectancy. By use of a cover which is completely liquid proof, problems of soiling or wetting of the internal core are avoided so that the mattress requires minimal servicing.

Claims (10)

1. A mattress comprising first and second layers of plastics foam laminated together to form a rectangular block, the first layer consisting of an open cell plastics foam of density lying in the range 33-40 kg/m3 and hardness in the range 100-150 Newtons, and the second layer consisting of an open cell plastics foam of density lying in the range 27-32 kg/m3 and hardness in the range 70-120 N, the block being enclosed fully in a cover made of a stretch fabric.

2. A mattress comprising first, second and third layers of plastics foam laminated together to form a rectangular block, the second, intermediate layer being made of an open cell plastics foam of density lying in the range 33-40 kg/m3 and hardness in the range 100-150 N, and both of the outer first and third layers being made of an open cell plastics foam of density lying in the range 27-32 kg/m3 and hardness in the range 70-120 N, the block being enclosed fully in a cover made of a stretch fabric.

3. A mattress as claimed in claim 2, in which said open cell plastics material is a combustion modified polyurethane foam.

4. A mattress as claimed in claim 2 or 3, in which the thickness of the intermediate layer is not less than 2" (5.08 cms).

5. A mattress as claimed in claim 2, 3 or 4, in which the thickness of the first and third layers is not less than 1" (2.54 cms) and not greater than 1" (3.81 cms).

6. A mattress as claimed in any of claims 2 to 5, in which the overall thickness of the block is not less than 5" (12.70 cms) and not more than 7" (17.78 cms).

7. A mattress as claimed in any of claims 1 to 6, in which the stretch fabric material of the cover is a weft knitted nylon fabric which is laminated to a layer of polyurethane film.

8. A mattress as claimed in claim 7, in which the polyurethane forming said film is ether-based.

9. A mattress as claimed in any of claims 1 to 8, in which the various layers of the mattress are connected together using a cured neoprene adhesive.

10. A mattress substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.