FOAM MATTRESS WITH SEAT

TECHNICAL FIELD The present invention relates to a foam mattress, which mattress comprises a head section, a middle section and a foot section and comprises a first layer of foam that at least comprises one layer of said head section, middle section and foot section, where said first layer of foam is manufactured from a foam of a first hardness, the mattress also comprising a second layer of foam that at least partly comprises said middle section and that is manufactured from a foam of a second hardness, whereby the second hardness of the second layer of foam is harder than the first hardness of the first layer of foam.

STATE OF THE ART AND PROBLEM In the medical service it is common to use beds the bed bottom of which is split in order to be able to raise the head end of the bed such that the patient will be able to sit up in the bed. In order to be able to offer a comfortable sitting position, the bottom of the bed is moreover commonly split in four with one joint above the seat of the patient, one joint just below and one joint at the knees of the patient. Given that the patients often spend a lot of their waking time sitting in the bed, the load will be much higher on the part on which the patient sits than on the rest of the mattress. This is of course also true for mattresses that are used in other contexts and that are often used in sitting position. It has now been shown that foam mattresses that are used in medical care, by patients that often sit in the bed, are subjected to increased wear on the middle thereof, i.e. the position in which the foam mattress is exposed to an increased pressure when the patient sits up. Given that the mattress is adapted to lying persons, this means that the mattress is prematurely worn out. Accordingly a need exists for a mattress of improved durability but which still provides a comfortable lying function.

Another object is to be able to provide a flexible mattress that can be adapted to the user's need of support.

It is yet another object to be able to provide a mattress that is easy to use for the nursing staff and that minimizes the risk of erroneous use of the mattress.

BRIEF ACCOUNT OF THE INVENTION

It is an object of the present invention to eliminate or at least minimize the above mentioned problems, which can be achieved by a foam mattress, which mattress comprises a head section, a middle section and a foot section and comprises a first layer of foam that at least comprises one layer of said head section, middle section and foot section, where said first layer of foam is manufactured from a foam of a first hardness, the mattress also comprising a second layer of foam that at least partly comprises said middle section and that is manufactured from a foam of a second hardness, whereby the second hardness of the second layer of foam is harder than the first hardness of the first layer of foam. The mattress is characterised in that it is arranged to be used in a bed the bed bottom of which is adjustable at least into a lying position and a sitting position, said first layer of foam constituting an upper layer arranged to form a lying module that carries a person lying in the bed, said second layer of foam constituting a lower layer forming a sitting module that is positioned essentially centrally in the middle section, whereby an improved sitting comfort and an increased support is obtained when the person sits in the bed.

Thanks to the invention the advantage is achieved that a mattress of improved durability can be provided. Yet another advantage is that the mattress provides improved comfort for the person sitting on the mattress, while retaining or improving the lying comfort. The mattress is comparatively simple in design, which gives a cost benefit.

According to further aspects of the invention:

- the sitting module comprises a lower layer of said middle section and comprises 25- 50% of the length of the mattress and is essentially centrally positioned, whereby the mattress can be used in different types of beds adapted for differently sized persons,

- the sitting module has an extension that is symmetrical in the longitudinal direction of the mattress,

- the sitting module has a symmetrical extension in the cross-direction of the mattress, which extension comprises at least 50%, more preferably at least 75% and most preferred 100% of the width of the mattress, whereby an improved sitting comfort can be achieved for a person sitting in the bed when the bed in sitting position,

- the sitting module is an essentially rectangular layer of even thickness in the middle section, whereby the sitting module achieves the same properties in the cross-direction and the mattress becomes easy to manufacture and whereby an efficient utilisation of the material can be achieved,

- the middle section comprises a first supporting wing that extends from the sitting module towards the head section of the mattress, the extension of the first supporting wing in the cross-direction corresponding to the extension of the sitting module, where at least a part of the supporting wing has a thickness that gradually decreases in a direction towards said head section, whereby an improved comfort can be achieved.

- additional comfort can be achieved by providing the foam mattress with a corresponding supporting wing that extends towards the foot section of the mattress. This also eliminates the risk of the mattress being turned in the wrong direction,

- the supporting wing consists of the foam quality of higher hardness and by at least partly allowing the supporting wing to extend gradually upwards, inwards into the mattress, in a convex portion, an ergonomic supporting wing can be achieved which offers good support for the curve of the back/the waist when the person is lying down. The supporting wing will also provide somewhat increased stability when the person is sitting in bed. The supporting wing preferably ends with an essentially straight portion that runs mainly in the longitudinal direction of the mattress,

- by designing the foam mattress such that the thickness of said first layer of foam in the portion above the supporting wing is less than above a middle portion of the sitting module and the first layer of foam at least partly surrounds the supporting wing, a mattress of very good lying comfort can be achieved at the same time as the sitting module provides improved sitting comfort,

- by allowing the supporting wing to form a continuous, integral part of the sitting module, a beneficial production economy can be achieved and the mutual positions of the portions can be guaranteed.

- the first layer of foam has a hardness Hl in the range 50 < Hl < 150 N, preferably 100- 140 N and most preferred 110- 130 N, and the second layer of foam has a hardness of 150 < H2 < 300 N, preferably 170-250 N and most preferred 180-220 N, according to a standard test method called ISO 2439 B, whereby a foam mattress can be achieved with good balance between sitting comfort and lying comfort, without the foam mattress becoming unnecessarily thick, at the same time as a beneficial production economy can be achieved as such foams are conventional among foam producers,

- the first layer of foam is given a thickness of 4-50 cm, preferably 8-25 cm, most preferred about 10-15 cm, and the second layer of foam is given a thickness in the range 2-25 cm, preferably 3-8 cm, most preferred 4-6 cm,

- the sitting module is joined together with the lying module, e.g. by gluing and/or welding, whereby an overlay mattress is achieved which is easy and safe to use.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in greater detail with reference to the attached drawing figures, of which:

Fig. 1 shows a planar view of a mattress according to the invention, as seen from above,

Fig. 2 shows a longitudinal cross-section of a foam mattress according to the invention, in a first embodiment, Fig. 3 shows a longitudinal cross-section of a detail of a foam mattress according to the invention, in a preferred embodiment, Fig. 4 shows a side view of a foam mattress according to the invention, in use, and

Fig. 5 shows a longitudinal cross-section of a foam mattress according to an alternative embodiment.

DETAILED DESCRIPTION OF THE INVENTION Fig. 1 shows a planar view of a foam mattress 1 according to the invention, as seen from above. For the sake of simplicity, the mattress will be described as if divided in three longitudinal sections; a head section 3, a middle section 4 and a foot section 5, the demarcations being indicated by imaginary lines C ₁ and C ₂ . As is clear from the names of these sections, the head section comprises the portion of the mattress upon which a person rests at least his/her head and preferably also his/her shoulders. The foot section comprises the lower portion of the mattress upon which the feet and also the legs are positioned. The middle section forms the largest portion of the mattress and comprises the position of the torso and the thighs and extends between the head section and the foot section. These sections should by no means be seen as delimiting for the mattress as such, but are just a way to facilitate the disclosure of the mattress. Naturally, there may also exist subsections that however need not be mentioned here. Moreover, these sections can be surrounded by a frame or be supplemented by other sections in the upper and lower ends, not shown here. These optional sections preferably form integral portions of the mattress. The figure shows a cross-sectional line A-A from which the structure of the mattress will be described in the following figures.

Fig. 2 shows a longitudinal section along line A-A, of a foam mattress 1 according to a first embodiment of the invention. Here, the mattress consists of a lying module 6 in the form of a first layer of foam 7 that in this very simple embodiment comprises the entire above mentioned head section 3 and foot section 5 as well as an upper layer of the middle section 4. This first layer of foam 7 is manufactured from a foam of a first hardness Hl, in the range 50 < Hl < 150 N, preferably 100-140 N and most preferred

110-130 N, according to a standard test method called ISO 2439 B. When the user has a weight of 40-130 kg, this first layer of foam 7 has a thickness T _L1 in the range 4-50 cm, preferably 8-25 cm and most preferred 10-15 cm. Generally, the higher the weight of the user, the more important it is to correctly choose the hardness and the thickness of the sitting module.

The middle section 4 of the mattress comprises a sitting module 8 positioned on the underside of the mattress in the form of a lower, second layer of foam 9 of a second hardness H2 that is higher than said first hardness Hl . By the second hardness H2 of said second layer of foam 9 being 150 < H2 < 300 N, preferably 170-250 N and most preferred 180-220 N at a thickness T _L2 of the second layer of foam 9 in the range of 2- 25 cm, preferably 3-8 cm, most preferred 4-6 cm, the sitting and lying comfort of the mattress can be optimised.

The sitting module 8 comprises 25-50%, preferably 25-40% and even more preferred 25-35% of the length L of the mattress and is positioned essentially centrally. Suitably, the sitting module 8 has an extension that is symmetrical in the longitudinal direction as well as in the cross-direction of the mattress, in order to avoid the risk of the mattress being turned in the wrong direction. The sitting module 8 comprises at least 50%, more preferred at least 75% and most preferred at 100% of the width B of the mattress and is positioned such that it comprises the part of the mattress upon which the seat of a person sitting in the bed is positioned when the bed is in a sitting position. The simplest way of forming the sitting module is as an essentially rectangular layer of even thickness of said middle section 4, which is most easily attached to the first layer 7 of foam by gluing, although other ways of joining the layers can be used, as is known to the skilled person. The entire mattress is covered in an elastic and pliable cover, not shown.

Fig. 3 shows a longitudinal section along line A-A, of the middle section 4 of a mattress 1 according to a preferred embodiment of the invention. As is shown in the figure, the sitting module 8 comprises supporting wings 10, 11 that extend towards the head section and the foot section, respectively. Preferably, the extension in the cross-direction of the respective supporting wings 10, 11 corresponds to the extension of the sitting module 8. Suitably, the supporting wing has a gradually decreasing thickness in the direction towards said head and foot section, respectively, at least in the area closest to the middle portion 12 of the sitting module. It is furthermore an advantage if the supporting wings 10, 11 at least partially extend gradually upwards, inwards into the

mattress in a convex portion, whereby an ergonomic supporting function can be achieved by the sitting module 8 thereby comprising a deeper part in the middle portion 12, where the pelvis/hips of a person should be positioned. The supporting wings 10, 11 form a more shallow part of the sitting module and thereby a supporting function can be achieved for the curve of the back/the waist and the thighs, respectively. Suitably, the convex portion changes to a straight portion that can be given a desired extension in the longitudinal direction of the mattress, not longer however than for the shoulders to be able to sink down in the mattress. Suitably, the supporting wing is manufactured from a foam of the same hardness as the middle portion of the sitting module. The middle portion 12 of the sitting module forms 40-80% of the total length X of the sitting module. Suitably, the middle portion 12 has a length Xi of about 30-60 cm, preferably about 40 cm and the respective supporting wings 10, 11 have a length X ₂ of 10-30 cm, preferably about 20 cm.

In the preferred embodiment according to Fig. 3, the thickness of the first layer of foam 7 varies along the sitting module 8. In the part above the middle portion 12 of the sitting module, i.e. the deeper part, the first layer of foam 7 has a first thickness T _L1 that is larger than a second thickness T ¹ _L1 in the parts above the supporting wings 10, 11. hi the part at the supporting wings 10, 11, there is also a lower, third layer of foam 12 that together with the first layer of foam 7 encloses the supporting wings 10, 1 1. In this preferred embodiment of the mattress, the first layer of foam 7 has a first thickness Tn of about 8 cm at a hardness Hl of 120 N. The thickness Tu of the second layer of foam 9 in the middle portion 12 is about 4 cm thick at a hardness H2 of 190 N.

Suitably, the third layer of foam forms an integral part of the first layer of foam and preferably the same type of foam is used in order to enable easy manufacturing. It is furthermore not a disadvantage if the middle portion 12 of the sitting module is allowed to bulge out somewhat at the underside of the mattress, as is shown in the figure. Hereby, the consumption of material in the first layer of foam 7 can be decreased without negatively influencing the lying comfort. The mattress according to the invention will on the contrary contribute to the ability to choose the hardness of the sitting module 8 such that the second layer of foam 9 gets somewhat compressed when the person lies on the mattress, whereby an increased support can be achieved for the curve of the back/the waist and the thighs of the patient also when the patient is lying down.

In a preferred embodiment, the supporting wings 10, 11 form a continuous integral part of the sitting module 8, which has proven to give some production advantages but which also means that the supporting wings 10, 11 are kept in place in relation to the middle portion 12 of the sitting module, thereby ensuring good function of the mattress. The function and the user friendliness also benefit from the sitting module 8 being fixedly connected to the lying module 6, such as by gluing and/or welding or other manners known to the person skilled in the art.

Fig. 4 shows a side view of a preferred embodiment of a mattress according to the invention, when used in a sitting position. The front supporting wing 10 extends a distance up along the back and gives improved support for the curve of the back/the waist of the person. It is advantageous to form the mattress such that the supporting wing changes to the thicker middle portion 12 of the sitting module level with the joint 13 for the backrest of the bottom of the bed. When the backrest is raised, the pressure is redistributed such that the major part of the load ends up on the middle portion 12 of the sitting module. By choosing a suitable hardness and thickness of the two layers of foam 7, 9, the mattress can be designed such that the sitting module 8 preferably is active when the patient is sitting up, while the lying module 6 preferably is active when the patient is lying down. For an optimised lying comfort, the lying module should give enough support for a lying person without the middle portion of the sitting module being experienced as dominant. It is however advantageous for the two supporting wings 10, 11 to be allowed to give some support for the curve of the back/the waist and the upper parts of the legs of the person. In case the mattress is used in medical care, it may suitably be supplemented by a top overlay mattress 14 which somewhat reduces the shearing forces that may arise between the skin and the underlying body tissue and that in time may give rise to injuries. In that case, the thickness of the first layer of foam 7 can be reduced.

Fig. 5 shows a longitudinal section of a mattress 1 according to the invention, in an alternative embodiment. The mattress comprises a sitting module 8 with supporting wings 10, 11, but the sitting module has been given a simplified shape and for the sake of simplicity it has been positioned on the underside of the lying module 6.

ALTERNATIVE EMBODIMENTS

The invention is not limited to that described above but may be varied within the scope of the claims. It should be understood that a mattress with the lying module and/or the

sitting module consisting of a combination of a plurality of layers of foam of varying hardness is comprised in the scope of the invention. The first layer of foam may for example be divided into a plurality of sublayers of different hardness. In that case, the sublayer closest on top of the sitting module can be 4-6 cm thick and have a hardness of about 120 N. On top of this, a somewhat softer upper sublayer can be arranged with the purpose of increasing the comfort or giving particularly preferred medical properties such as pressure relief. The upper sublayer can have a hardness of 80-100 N at a thickness of 4-6 cm and may furthermore be cut in a manner known to the person skilled in the art, for example cut in cubes, which will result in particular advantages for the user. The mattress may also be provided with an additional layer of foam that extends along the entire bottom of the mattress as well as under the sitting module. This additional bottom layer will give an additional possibility of optimizing the supporting properties of the mattress and suitably it can be used by heavier users as it will allow extra support and improved comfort over the entire mattress, for such users. The additional bottom layer may for example be given a thickness of about 3 cm at a hardness of about 190 N, which will make the mattress particularly suited for user weights of above 200 kg. The person skilled in the art will realise that a subdivided first layer of foam can be combined with an additional bottom layer and naturally that the mattress can be designed to have either a subdivided first layer of foam or an additional bottom layer.

It is furthermore realised that the sitting module can be provided with only a single supporting wing. The supporting wing and the sitting module can be manufactured from foams of different hardness, whereby the supporting wing can be given properties that fulfil more and other needs of the person. The third layer of foam, that together with the first layer of foam encloses the supporting wing, can be of a third hardness in order to further optimize the supporting properties. It is also realised that the sitting module is not limited to have a rectangular shape but that other shapes of the sitting module can be suitable too. The sitting module may for example be round, elliptic, triangular, heart shaped or kidney shaped. Naturally, the thickness and the hardness of the foam within the middle portion of the sitting module can varied if varying properties are desired within the sitting module, thereby to give different properties in different places.

It is realised that it is within the scope of the invention that all methods known to the person skilled in the art of joining the different parts of the mattress are comprised and that the methods mentioned in the description are examples only of suitable methods.

In an alternative embodiment, the mattress can be formed with a detachable sitting module 8. Hereby a foam mattress is achieved which offers the possibility of individualised adaptation depending on the weight of the user. Such a mattress also offers the possibility to exchange the sitting or lying module in case it has become worn. This embodiment will also allow for a simplified production of the mattress. The sitting module and the lying module are fixed in relation to each other by a releasable joint, such as a Velcro joint, a zip fastener and/or buttons and/or by a mattress cover that is arranged to keep the sitting module and the lying module in their respective mutual positions. It is furthermore realised that the adaptation in shape of the sitting module and the lying module in relation to each other will contribute to the mutual fixation of the parts in relation to each other, and that sitting modules of other shapes than the one shown here naturally can be used to achieve the same object. The undersides of the supporting wings can for example be provided with bulges, as if it was barbed, to engage with corresponding depressions in the layer of foam that encloses the underside of the supporting wings.

The mattress according to the invention has been described from the viewpoint of use within medical care. It should be understood that the mattress according to the invention is suitable not only for such users but that it also can be used by persons that for other reasons spend a lot of time in bed. Private use of the mattress is also within the scope of the invention, in newer beds that increasingly comprise a sitting function.